Patent Publication Number: US-11644497-B2

Title: Charge storage with electrical overstress protection

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/743,878, filed Jan. 15, 2020, which is a continuation U.S. application Ser. No. 15/801,132, filed Nov. 1, 2017, issued Feb. 11, 2020 as U.S. Pat. No. 10,557,881, which is a continuation of U.S. application Ser. No. 14/671,767, filed Mar. 27, 2015, issued Jan. 16, 2018 as U.S. Pat. No. 9,871,373, the disclosures of each of which are hereby incorporated by reference in their entireties herein. 
    
    
     BACKGROUND 
     Technical Field 
     The disclosed technology relates to electronic systems, and, more particularly, to taking action responsive to and/or in anticipation of an electrical overstress event. 
     DESCRIPTION OF THE RELATED TECHNOLOGY 
     Certain electronic systems can be exposed to electrical overstress events. Such events can cause damage, such as thermal damage, as a result of an electronic device experiencing a current and/or a voltage that is beyond the specified limits of the electronic device. For example, an electronic device can experience a transient signal event, or an electrical signal of short duration having rapidly changing voltage and high power. Transient signal events can include, for example, electrostatic discharge (ESD) events arising from the abrupt release of charge from an object or person to an electronic system, or a voltage/current spike from the electronic device&#39;s power source. 
     Electrical overstress events, such as transient signal events, can damage integrated circuits (ICs) due to overvoltage conditions and high levels of power dissipation in relatively small areas of the ICs, for example. High power dissipation can increase IC temperature, and can lead to numerous problems, such as gate oxide punch-through, junction damage, metal damage, surface charge accumulation, the like, or any combination thereof. 
     SUMMARY OF CERTAIN INVENTIVE ASPECTS 
     One aspect of this disclosure is an apparatus that includes an electrical overstress protection device, a detection circuit electrically coupled to the electrical overstress protection device, and a memory. The detection circuit is configured to detect an occurrence of an electrical overstress event. The memory is configured to store information indicative of the electrical overstress event detected by the detection circuit. 
     Another aspect of this disclosure is an apparatus that includes an electrical overstress protection device, a detection circuit electrically connected to the electrical overstress protection device, and a reporting circuit in communication with the detection circuit. The detection circuit is configured to detect an occurrence of an electrical overstress event. The reporting circuit is configured to provide information indicative of the electrical overstress event detected by the detection circuit. 
     Another aspect of this disclosure is an electronically-implemented method of recording information associated with an electrical overstress event. The method includes detecting, using detection circuitry electrically connected to an electrical overstress protection device, an occurrence of an electrical overstress event. The method also includes recording information associated with the occurrence of the electrical overstress event to a memory. 
     Another aspect of this disclosure is an apparatus that includes an electrical overstress steering device and a storage element configured to store charge associated with an electrical overstress event, in which the electrical overstress steering device is configured to provide energy associated with the electrical overstress event to the storage element. 
     The electrical overstress device can be disposed between a contact, such as a pin, of an electronic device and the storage element. An electrical overstress protection device can be electrically connected to the contact to provide electrical overstress protection. The storage element can include, for example, a capacitor. The electrical overstress steering device can be electrostatic discharge steering device and electrical overstress event can be an electrostatic discharge event. 
     Another aspect of this disclosure is an apparatus that includes a proximity sensor, an electrical overstress configuration circuit, and an electrical overstress protection circuit. Responsive receiving an indication of proximity from the proximity sensor, the electrical overstress configuration circuit can configure the electrical overstress protection circuit. For example, the electrical overstress configuration circuit can pre-trigger and/or prime the electrical overstress protection circuit. 
     Another aspect of this disclosure is an apparatus that includes a proximity sensor, a storage element, a storage element configuration circuit, and an electrical overstress steering device. The storage element can store charge associated with an electrical overstress event, in which the electrical overstress steering device is configured to provide energy associated with the electrical overstress event to the storage element. Responsive receiving an indication of proximity from the proximity sensor, the storage element configuration circuit can configure the storage element. 
     For purposes of summarizing the disclosure, certain aspects, advantages and novel features of the inventions have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a schematic block diagram of an electronic system that includes electrical overstress detection circuitry, energy harvesting circuitry, and a proximity sensor according to an embodiment. 
         FIG.  1 B  is a schematic diagram of an illustrative electronic device that includes electrical overstress detection circuitry according to an embodiment. 
         FIGS.  2 A to  2 D  illustrate example electrical overstress protection devices that can be implemented in one or more embodiments. 
         FIG.  3    is a schematic diagram of a portion of an illustrative electronic device configured to detect an electrical overstress event at a pin of the electronic device according to an embodiment. 
         FIG.  4    is a schematic diagram of a portion of an illustrative electronic device configured to detect electrical overstress events across a storage element according to an embodiment. 
         FIG.  5    is a schematic diagram that includes a detection circuit and an electrical overstress protection device according to an embodiment. 
         FIG.  6    is a schematic diagram that includes a detection circuit and an electrical overstress protection device according to another embodiment. 
         FIG.  7    is a schematic diagram that includes a detection circuit and an electrical overstress protection device according to another embodiment. 
         FIG.  8    is a schematic diagram that includes a detection circuit and an electrical overstress protection device according to another embodiment. 
         FIG.  9    is a schematic diagram of an illustrative circuit that is configured to detect and store information associated with electrical overstress events according to an embodiment. 
         FIG.  10    is a schematic diagram of a portion of an electronic device with an electrical overstress event detection circuit according to an embodiment. 
         FIG.  11    is a diagram of stacked dies including a die that includes functional safety circuitry according to an embodiment. 
         FIG.  12    is a diagram of a system in a package that includes functional safety circuitry according to an embodiment. 
         FIG.  13    is a diagram of a system that includes functional safety circuitry according to an embodiment. 
         FIG.  14    is a schematic diagram of an illustrative electronic device that is configured to store charge associated with an electrical overstress event according to an embodiment. 
         FIG.  15    is a schematic diagram of an illustrative electronic device that is configured to store charge associated with an electrical overstress event and to detect an occurrence of the electrical overstress event according to an embodiment. 
         FIG.  16    is a schematic diagram of a portion of an illustrative electronic device configured to store charge associated with an electrical overstress event according to an embodiment. 
         FIG.  17    is a schematic diagram of a portion of an illustrative electronic device configured to store charge associated with an electrical overstress event in a bank of storage elements according to an embodiment. 
         FIG.  18    is a schematic diagram of a circuit configured to store charge associated with an electrical overstress event according to an embodiment. 
         FIG.  19    is a schematic diagram of a circuit configured to store charge associated with an electrical overstress event according to another embodiment. 
         FIG.  20    is a schematic diagram of a circuit configured to store charge associated with an electrical overstress event according to another embodiment. 
         FIG.  21    is a schematic diagram of a circuit configured to store charge associated with an electrical overstress event according to another embodiment. 
         FIG.  22    is a schematic diagram of a circuit configured to store charge associated with an electrical overstress event according to another embodiment. 
         FIG.  23 A  is a plan view of an example layout of an electrical overstress protection device according to an embodiment. 
         FIG.  23 B  is a plan view of another example layout of an electrical overstress protection device according to an embodiment. 
         FIG.  23 C  is a plan view of another example layout of an electrical overstress protection device according to an embodiment. 
         FIG.  24    illustrates another electrical overstress protection device where the current surge is conducted vertically through to the layer below according to an embodiment. 
         FIG.  25    illustrates an example of a vertically integrated system with scaled up structures capable of harnessing an electrical overstress event for storing charge according to an embodiment. 
         FIG.  26    is a schematic diagram of a vertically integrated system that includes electrical overstress protection and energy harvesting circuitry according to an embodiment. 
         FIG.  27    is a schematic diagram of a vertically integrated system that includes electrical overstress protection and energy harvesting circuitry on a single chip according to an embodiment. 
         FIG.  28    illustrates a die with electrical overstress protection devices, storage elements, and processing circuitry according to an embodiment. 
         FIG.  29    illustrates a die with electrical overstress protection devices, storage elements, and processing circuitry according to another embodiment. 
         FIGS.  30 A and  30 B  illustrate an embodiment of a mobile device that includes an external casing having conduits embedded within the external casing according to an embodiment. 
         FIG.  30 C  illustrates an embodiment of a wearable device that includes an external casing having conduits embedded within the external casing according to an embodiment. 
         FIG.  31    illustrates examples of conductive structures in an opening of a package that can provide electrical connections to ESD protection devices according to various embodiments. 
         FIG.  32    illustrates a system that includes a rotating shaft and a charge harvesting system according to an embodiment. 
         FIG.  33 A  illustrates a rotating shaft having a layer of material for enhancing electrostatic charge and/or field generated by a rotating shaft and a charge harvesting system according to an embodiment.  FIG.  33 B  illustrates that the layer of material incorporated on a rotating shaft can have a non-uniform width in certain embodiments.  FIG.  33 C  illustrates a selected surface topography of the layer of material of the energy harvesting system according to an embodiment.  FIG.  33 D  illustrates a surface finish on the layer of material of the energy harvesting system according to an embodiment. 
         FIG.  33 E  is a block diagram of another context in which energy harvesting can be implemented according to an embodiment. 
         FIG.  34    is a schematic block diagram of an illustrative electronic device that can condition or initiate electrical overstress protection in response to proximity sensing information according to an embodiment. 
         FIG.  35    is a schematic block diagram of an illustrative electronic device that can configure a storage element arranged to store energy associated with an electrical overstress event using proximity sensing information according to an embodiment. 
         FIG.  36    illustrates an example electronic device with energy harvesting and storage and/or EOS event detection circuitry according to an embodiment. 
         FIG.  37    illustrates an example electronic device with energy harvesting and storage and/or EOS event detection circuitry according to an embodiment. 
         FIG.  38    illustrates an example electronic device with energy harvesting and storage and/or EOS event detection circuitry according to an embodiment. 
         FIG.  39    illustrates an example electronic device with energy harvesting and storage and/or EOS event detection circuitry according to an embodiment. 
         FIG.  40    illustrates an example electronic device with energy harvesting and storage and/or EOS event detection circuitry according to an embodiment. 
         FIG.  41    illustrates an example electronic device with energy harvesting and storage and/or EOS event detection circuitry according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
     The following detailed description of certain embodiments presents various descriptions of specific embodiments. However, the innovations described herein can be embodied in a multitude of different ways, for example, as defined and covered by the claims. In this description, reference is made to the drawings where like reference numerals can indicate identical or functionally similar elements. It will be understood that elements illustrated in the figures are not necessarily drawn to scale. Moreover, it will be understood that certain embodiments can include more elements than illustrated in a drawings and/or a subset of the illustrated elements. Further, some embodiments can incorporate any suitable combination of features from two or more drawings. The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claims. 
     Structures for protection against electrostatic discharge (ESD) or other electrical overstress events on an integrated circuit, such as a silicon chip, can occupy about 15% to about 20% of total integrated circuit area in certain applications. Over the last 40 years, structures used for the conduction, discharge/dissipation of static charge/ESD events have improved such that integrated circuits are able to withstand higher currents, higher voltages, transient events, etc. Such ESD protection structures can divert a signal surge to ground. While this disclosure may discuss ESD protection circuits and ESD events for illustrative purposes, it will be understood that any of the principles and advantages discussed herein can be applied to any other electrical overstress (EOS) condition. EOS events can encompass a variety of events including transient signal events lasting about 1 nanosecond or less, transient signal events lasting hundreds of nanoseconds, transient signal events lasting on the order of 1 microsecond, and direct current (DC) overstresses. 
     In this disclosure, detecting/recording/reporting electrical overstress events, harvesting energy associated with electrical overstress events, and configuring electrical overstress protection circuits responsive to an indication that an electrical overstress is likely to occur are disclosed. The principles and advantages of any one of these concepts can be applied in connection with one or more of the other concepts. 
     Typical ESD protection circuits can protect internal circuits from potentially damaging ESD events without storing or otherwise reporting that an ESD event has occurred. As such, information associated with the occurrence of an ESD event is unavailable to an electronic system. In certain applications, there is a need for reliable circuit operation. For instance, when electronics in a car or other vehicle fail, such failures can threaten safety of a driver and/or a passenger. As another example, it can be desirable for electronics in healthcare applications, such as heart rate monitoring applications, to reliably detect a change in a physiological parameter so that proper action can be taken responsive to detecting such a change. When circuits in such healthcare applications fail, health can be adversely impacted. In applications where there is a need for reliable circuit operation, unknown potential damage to critical circuits can be problematic. 
     Aspects of this disclosure relate to detecting and recording electrical overstress events. An electrical overstress event can be detected and information indicative of the electrical overstress event can be stored to memory and/or be reported external to an electronic device. Detection circuitry can detect an electrical overstress event and, in some instances, an intensity of the electrical overstress event. Physical memory can store information indicative of an intensity of an overstress event and/or a number of occurrences of electrical overstress events. The detection circuitry and the memory can be part of the same integrated circuit (e.g., on the same die and/or within the same package) as the electrical overstress protection circuitry. In an embodiment, the detection circuit and the memory can be implemented by a combined detection and memory circuit. 
     The information associated with the electrical overstress event stored in the memory can be useful for functional safety purposes. For instance, this information can serve as indication of wear or lifespan of the device, indicate that an electronic device is potentially damaged, that data provided by an electronic device is potentially corrupt, that a measurement provided by an electronic device is potentially inaccurate, the like, or any combination thereof. The information associated with an electrical overstress event can be reported to provide information about the functional safety of electrical overstress protection circuitry and/or of internal circuit(s) protected by the electrical overstress protection circuitry. The electronic overstress detection and reporting circuitry can provide an early indication of adverse conditions, analogous to a canary in a coal mine. In harsh environments, the electronic overstress detection and reporting circuitry can provide indicators of a lifespan of an electronic device and/or an electronic system. Tracking the lifespan of an electronic device by recording and reporting electrical overstress events can lead to better reliability of critical circuit and/or predictability of time for replacement. This can be advantageous in a variety of applications, such as in preventing failures in vehicles that can threaten safety and/or in healthcare applications. 
     For instance, a custom semiconductor die operating in an electronic device can record information indicative of an occurrence of an electrical overstress (e.g., overvoltage and/or ESD) event in memory of the semiconductor die. The occurrence of the overstress event may indicate that there is a fault within the electronic device. The occurrence of the electrical overstress event may indicate that external protection circuitry, i.e., circuitry connected to the custom semiconductor die, such as separate protection circuitry on another chip or on a board, is faulty such that a semiconductor die experiences surges and/or current spikes outside of a specification for circuitry to be protected, which can be on the custom semiconductor die or outside of the custom semiconductor die. As an example, a solder joint for the external protection circuitry can degrade and thus provide less than desirable protection from an overvoltage event. The semiconductor die can provide the information indicative of the occurrence of the electrical overstress event external to the semiconductor die and/or external to an electronic device that includes the semiconductor die. This can serve as a diagnostic to inform an electronic system that electrical overstress protection circuitry is no longer functioning at a desired level. 
     A specialized semiconductor die can be devoted to handling electrical overstress, including detection and recording information indicative of overstress events in a memory of the semiconductor die. The specialized semiconductor die can also serve to harvest energy associated with EOS events and/or to provide EOS protection. In certain implementations, recording functions can be implemented on a different semiconductor die than EOS protection functions. 
     In some instances, an integrated circuit may have a limited/defined life span. This can result from, for example, being in a harsh electrical environment. The electrical overstress detection and reporting circuitry can provide information about an intensity of an electrical overstress event and/or a number of occurrences of electrical overstress events as flags to an electronic system. After a defined number of electrical overstress events have been detected, the electronic system can provide a flag that an electronic device has a reduced lifespan. Such a flag can indicate that the electronic device is due for replacement relatively soon or within a defined period of time. Tracking the lifespan of a device can lead to better reliability of critical circuits and/or a better prediction of time for replacement. 
     Information indicative of electrical overstress events can be provided externally to an electronic device that experiences the electrical overstress events or to separate monitoring circuitry or devices. For instance, wireless and/or inductive circuits can provide signal remote to the electronic device to provide a warning and/or a status of the heath of the electronic device or an electronic system that includes the electronic device. Such warnings can provide indicators of the life span of the system and/or general system health. This can enable planning for a new/replacement electronic device to be included in the electronic system. These principles and advantages can be applied to a variety of electronic systems, such as electronic systems in cars and/or other vehicles and/or in healthcare applications. 
     Aspects of this disclosure relate to storing charge associated with electrical overstress events, such as ESD events. ESD protection circuits, which can protect internal circuits from overvoltage events, typically divert charge to ground. A significant amount of energy can be associated with an ESD event. Instead of dissipating all charge associated with ESD events, a significant amount of the charge can be stored in a storage element, such as capacitor(s), and the stored charge can then be used by the electronic system. For example, such storage elements can be employed to supply power for events such as periodic wireless transmissions, to smooth out power delivery, to supplement or replace battery power, or any combination thereof. To facilitate storing change associated with ESD events, ESD protection structures can be scaled up (e.g., configured to carry more current and/or conduct/funnel more energy). While ESD events may be described in connection with harvesting change, it will be understood that charge can be harvested from any other EOS event in accordance with the principles and advantages discussed herein. 
     At a system level, electrical overstress protection circuits can be segregated (e.g., chips or layers in a package can be devoted to EOS event handling) and/or scaled up. Such electrical overstress protection circuits can be configured such that they provide system level electrical overstress protection; energy associated with electrical overstress events can be routed to a storage element; and/or EOS events can be detected and recorded. Charge stored by the storage element can be subsequently used within the system. In some instances, system level electrical overstress protection circuits and storage elements that store harvested energy from electrical overstress events can be implemented in industrial applications or other instances where current surges or other electrical overstress events are expected. In such instances, an electronic system can be arranged to harvest charge from moving/rotating mechanisms prone to generation of static charge, for example. 
     In situations where an electronic device operates intermittently, the charge associated with an electrical overstress event that is stored by a storage element can be used to carry out another specific/defined function. For example, responsive to an ESD event, the harvested charge can be used to activate circuitry and record, for example, that an ESD event has occurred. Similarly, in situations where temporary/transient charge harvested from, for example, an ESD event is sufficient to carry out a task, an electronic device can carry out the task using the harvested charge. In certain applications, responsive to an ESD event, harvested charge can be used to activate circuitry and record information associated with the ESD event, for example, in accordance with the principles and advantages discussed herein associated with detecting an EOS event. 
     At a micro level, if 15% to 20% of die area that is already consumed by ESD protection circuitry is used to reduce power consumption of a semiconductor chip and there are a number of such chips within an electronic system, then over power consumption and system efficiency can be significantly improved by storing and subsequently using charge associated with an ESD event. For example, even a relatively small reduction in power consumption in a system with a relatively large number of chips (e.g., 500 chips) can add up over a long period of time (e.g., 5 to 10 years). The charge stored from harvesting can be employed to prolong battery life for the system, particularly for remote monitoring systems, to reduce power consumption from external sources, to power circuitry for recording EOS events, etc. 
     Harvesting charge associated with electrical overstress events can be implemented in a number of different contexts. For example, harvesting charge associated with ESD or other electrical overstress events can be implemented in certain industrial applications where a system could be constructed specifically to generate and store charge from moving and/or rotating parts. 
     A storage element that receives and stores energy associated with an electrical overstress event can include capacitor(s) and/or a battery. For instance, the storage element can include a super capacitor and/or thin film lithium ion battery. In these storage elements, leakage can be a concern, particularly when charge is intermittently harvested. 
     The storage element can be constructed to enhance (e.g., optimize) the flow of current into the storage areas. The storage element can be arranged such that current associated with an electrical overstress event can only flow in one direction during the storing phase, i.e., once the current flows into the storage area it does not flow back out the same path/conduit/channel. A level of charge stored by the storage element can be detected. The storage element can provide a signal indicative of how much charge is stored by the storage element. This signal can be used, for example, to indicate that the storage element has sufficient charge to provide to an electronic system. Information about the amount of charge stored by the storage element can be provided to other circuitry, such as remote circuitry external to a die that includes the storage element and/or remote to an electronic system that includes the storage element. The storage element can be activated or otherwise configured to be responsive to an indication that an EOS event is likely to occur. Different banks of storage components, such as capacitors, can be switched on and/or off as they charge. When a bank of storage components stores approximately a maximum amount of charge, charge associated with an EOS event can be routed to a different bank of storage elements. 
     In some applications, an electronic system can be powered by a combination of energy harvested from an electrical overstress event and a primary power source. When harvested energy is available, it can used to power the electronic system. When the stored energy is depleted, the system can switch to using the primary power source until harvested energy becomes available. When using an energy harvesting, voltage on a capacitor in the storage element can be monitored. Responsive to detecting that sufficient charge is stored on the capacitor, an interrupt can be provided to inform the system sufficient energy is available to transmit a signal from the electronic system. 
     Aspects of this disclosure relate to detecting proximity of an electrical field and configuring circuitry for EOS protection and/or harvesting energy from an EOS event responsive to detecting proximity. For instance, an EOS device can be conditioned, e.g., primed to trigger in response to an indication that an EOS event is likely to occur as a result of sensing proximity. Such features can be implemented in applications in which EOS events occur for very short durations, e.g., on the order of nanoseconds or a shorter duration of time, such that the charge from such rapid events may not be captured without predictive triggering. As another example, clamping of an ESD protection circuit can be actively controlled responsive to detecting proximity. In one more example, a storage element can be activated to capture charge associated with an EOS event responsive to detecting proximity. 
       FIG.  1 A  is a schematic block diagram of an electronic system  1  that includes electrical overstress detection circuitry, energy harvesting circuitry, and a proximity sensor according to an embodiment. The electronic system  1  can be a system on a chip as illustrated. The electronic system  1  is an example of a system that can implement features of EOS event detection, harvesting energy associated with EOS events, and configuring EOS devices and/or storage elements for harvested energy based on proximity sensing information. The electronic system  1  of  FIG.  1 A  includes EOS protection devices  2 , antennas  3  and  4 , an EOS event detection circuit  16 , a reporting circuit  18 , a storage element  144 , a data storage and processing circuit  5 , a communication bus transmitter circuit  6 , an antenna transmission circuit  7 , and a proximity sensor  342 . Some other embodiments can include more elements than illustrated and/or a subset of the illustrated elements. 
     EOS protection devices  2  can provide EOS protection for internal circuits of the electronic system. The EOS protection devices can implement one or more EOS sense devices, such as the EOS sense device  14  of  FIG.  1 B  or the ESD sense device  34  of  FIG.  3   , and one or more EOS steering devices, such as the ESD steering device  32  of  FIG.  3    or the EOS steering device  142  of  FIG.  14    or  FIG.  15   . 
     The EOS event detection circuit  16  can detect an occurrence of an EOS event. In some embodiments, the EOS detection circuit  16  can detect an intensity and/or a duration of an EOS event. The EOS event detection circuit  16  can provide information associated with an EOS event to the data storage and processing circuit  5  to be recorded. The EOS event detection circuit  16  can provide information associated with an EOS event to the antenna transmission circuit, which can transmit such information via the antenna  4 . The EOS event information can alternatively or additionally provide information associated with an EOS event to the communication bus transmitter  6  for transmission by way of a communications bus. In an embodiment, the communication bus transmitter  6  can be part of a transceiver. 
     The storage element  144  can storage energy associated with an EOS event. The storage element  144  can include one or more capacitors, for example. Charge stored by the storage element  144  can power other circuits of the electronic system  1  and/or be provided external to the electronic system  1 . 
     The proximity sensor  342  can sense proximity of an object and provide proximity information to the EOS event detection circuit  16  and/or the data stage and processing circuit  5 . Using proximity information, these circuits can configure one or more of the EOS protection devices  2  and/or the storage element. 
     Detecting Electrical Overstress Events 
     As discussed above, aspects of this disclosure relate to detecting electrical overstress events, such as ESD events. Information associated with EOS events can be recorded and/or reported. This can provide information about the functional safety of a circuit, a die, an integrated circuit system, or the like. Such information can be indicative of an intensity of an EOS event, a duration of an EOS event, and/or of a number of occurrences of EOS events detected. In some embodiments, information associated with EOS events can be indicative of a pulse width of an EOS event, as an EOS event can have an arbitrary waveform. Such information can be recorded for each EOS pulse and/or multiple records can be captured per pulse. Illustrative embodiments related to EOS event detection will now be discussed. 
       FIG.  1 B  is a schematic diagram of an illustrative electronic device  8  that includes electrical overstress detection circuitry according to an embodiment. The electronic device  8  can be implemented in a variety of applications. As some examples, the electronic device  8  and/or other electronic devices discussed herein can be included in an automotive electronics system, an avionics electronics system, a healthcare monitoring electronics system, or the like. As illustrated, the electronic device  8  includes an input contact  10 , an EOS protection device  11 , an EOS isolation device  12 , an internal circuit  13 , an EOS sense device  14 , a resistive element  15 , a detection circuit  16 , a memory  17 , a reporting circuit  18 , and an output contact  19 . The illustrated elements of the electronic device  8  can be included within a single package. The electronic device  8  can include more elements than illustrated and/or a subset of the illustrated elements. The electronic device  10  can be a die, for example. As such, in some instances, the illustrated elements of the electronic device  8  can be embodied on a single die. 
     The electronic device  8  is configured to receive an input signal at the input contact  10 , which can be an input pin as illustrated. The EOS protection device  11  is configured to provide protection from electrical overstress events. The illustrated EOS protection device  11  is configured to protect the circuitry electrically connected to the input contact  10  by diverting current associated with an EOS event to ground when a signal on the input contact  10  exceeds an EOS capability of the devices being protected, e.g., voltage breakdown. The EOS protection device  11  can protect the internal circuit  13  and the resistive element  15  from electrical overstress events. The EOS protection device  11  can also protect any other circuitry electrically connected to the input contact  10 . The EOS isolation device  12  is disposed between the internal circuit  13  and the pin in  FIG.  1 B . The EOS isolation device  12  can be, for example, a resistor. In  FIG.  1 B , the EOS protection device  11  is disposed between the input contact  10  and ground. The EOS protection device  11  can be disposed between the input contact  10  and any other suitable low voltage reference. The EOS protection device  11  can be an ESD protection device configured to provide ESD protection, for example. 
     The EOS sense device  14  is an EOS protection device. For instance, the EOS sense device  14  can be a high impedance scaled down version of the EOS protection device  11 . The EOS sense device  14  can be arranged to trigger at a signal level at which an EOS event is considered to occur. A relatively small percentage of the EOS event current can be provided through the resistive element  15  for purposes of detecting a magnitude of the EOS event. Accordingly, the signal provided to the detection circuit  16  by way of the EOS sense device  14  can be a scaled down version of a signal associated with an EOS event. 
     The resistive element  15  can be electrically coupled between the EOS sense device  14  and ground. This can provide a voltage drop such that a signal provided to the detection circuitry can be at a lower voltage than a voltage associated with the electrical overstress event, for example. The resistive element  14  can have a relatively low resistance (for example, about 1 Ohm in certain applications) and consequently the detection circuit  16  can receive a voltage signal that is at a lower voltage level (for example, a few volts) than a voltage associated with the electrical overstress event. The voltage drop provided by the resistive element  15  can prevent the detection circuit  16  from being damaged by the electrical overstress event. 
     As illustrated, the detection circuit  16  is electrically coupled to the EOS sense device  14  and configured to detect an occurrence of an electrical overstress event. For example, the detection circuit  16  can include a comparator configured to compare a voltage associated with an electrical over-stress event with a reference voltage. Such a comparator can generate an indication that an electrical overstress event has occurred. The detection circuit  16  can detect an intensity, such as a voltage level and/or a current level, associated with the electrical overstress event using one or more comparators and/or an analog-to-digital converter according to certain embodiments. 
     In certain embodiments, the detection circuit  16  can include circuitry, such as a counter circuit, to determine a duration of an EOS event. The duration of an EOS pulse can be indicative of an amount of energy associated with the EOS event. By detecting a duration of an EOS pulse, the detection circuit  16  can differentiate between different types of EOS events, such as long DC pulses versus short transient pulses. The different types of EOS events can have varying impacts on the functional safety of an electronic system exposed to such EOS events. Accordingly, detecting the duration of an EOS event can provide additional information about the functional safety of an electronic system in certain applications. 
     The detection circuit  16  can provide information indicative of an electrical overstress event to the memory  17 . The memory  17  can include any suitable physical circuitry to store such information, such as volatile memory or non-volatile memory. In certain embodiments, the memory  17  can include fuse elements. The memory  17  can store information indicative of the EOS event. For example, the memory  17  can store information indicative of an intensity of one or more EOS events, information indicative of a number of EOS events detected by the detection circuit  16 , information indicative of a type of EOS event, information indicative of a duration of an EOS event, the like, or any combination thereof. 
     The reporting circuit  18  can provide information indicative of one or more electrical over-stress events to external circuitry, such as circuitry external to the electronic device  1 . As illustrated, the reporting circuit  18  can receive such information from the memory  17 . In some other embodiments, the reporting circuit  18  can receive such information from the detection circuit  16  without the information being stored to memory of the electronic device  10  and report the information. The reporting circuit  18  can provide the information indicative of one or more electrical overstress events to the output contact  19 , which can be a pin as illustrated. According to certain embodiments, the reporting circuit  18  can wirelessly transmit such information and/or inductively transmit such information. The reporting circuit  18  can include the antenna transmission circuit  7  and/or the communication bus transmitter  6  of  FIG.  1 A  in certain embodiments. 
     Electrostatic discharge protection devices are examples of electrical overstress protection devices, such as the EOS protection devices shown in  FIG.  1 B  and/or other figures.  FIGS.  2 A to  2 D  illustrate example electrostatic discharge protection devices that can be implemented in one or more embodiments. Any of the electrostatic discharge protection devices illustrated in  FIGS.  2 A to  2 D  can be implemented in connection with any suitable embodiment related to electrical overstress event detection, harvesting energy associated with an electrical overstress event, configuring an electrical overstress protection device and/or a storage element responsive to an indication that an electrical overstress event is likely to occur, or any combination thereof. 
       FIG.  2 A  illustrates diode-based ESD protection devices  20   a .  FIG.  2 A  illustrates a unidirectional blocking junction diode  20   a   1 , series-forward blocking junction diodes  20   a   2  for proportional increase of forward-biased conduction and reverse blocking voltage, antiparallel low voltage drop-conduction and decoupling diodes  20   a   3 , and a high back-to-back diode-based bidirectional blocking device  20   a   4 . 
       FIG.  2 B  illustrates bipolar transistor-based ESD protection devices  20   b  including an NPN ESD device  20   b   1  and a PNP ESD device  20   b   2 . From collector to emitter (NPN) and emitter to collector (PNP), the bipolar transistors function as relatively high blocking voltage elements until reaching a breakdown voltage, at which point the device triggers and provides a low conduction path and high holding voltage between its terminals. In the opposite voltage polarity, a forward-biased junction is obtained. 
       FIG.  2 C  illustrates coupled unidirectional NPN and PNP thyristor-like ESD protection devices  20   c . The ESD protection devices shown in  FIG.  2 C  can be referred to as semiconductor-controlled rectifiers. In some instances, semiconductor-controlled rectifiers are silicon-controlled rectifiers (SCRs). The NPN and PNP thyristor-like ESD devices include configurations with: floating NPN base  20   c   1 , leading to a lower trigger voltage; an NPN in collector-emitter breakdown voltage mode with base-emitter resistance  20   c   2 , leading to an intermediate trigger voltage; a traditional configuration with fixed base resistance  20   c   3  for highest thyristor trigger voltage; and thyristor bipolar base external latch trigger and latch release control  20   c   4 . 
       FIG.  2 D  illustrates a coupled NPN-PNP-NPN bi-directional high blocking thyristor-like ESD protection device  20   d . The bidirectional breakdown voltage in this device can be closely defined by the base-emitter junction of the PNP device illustrated in the center of this device. 
     EOS events can be detected at various nodes in an electronic device in accordance with the principles and advantages discussed herein. The EOS event detection discussed herein can be sensed at a pin of an electronic device in certain embodiments.  FIG.  3    is a schematic diagram of a portion of an illustrative electronic device  30  configured to detect an electrostatic discharge event at a pin  31  of the electronic device  30  according to an embodiment. As shown in  FIG.  3   , an ESD event can occur at the pin  31 , which can be any suitable input/output (I/O) pin, and the ESD event can be sensed at the pin  31 . An ESD sense device  34  can be disposed between the pin  31  and ESD event detection circuit  36 , which is an example of the detection circuit  16  of  FIG.  1 B . The ESD event detection circuit  36  can provide information indicative of an occurrence of an ESD event to a memory and/or reporting circuit (not illustrated) similar to in  FIG.  1 B . In  FIG.  3   , resistor  35  is disposed between the ESD sense device  34  and ground. As illustrated, the resistor is also disposed between an input to the ESD event detection circuit  36  and ground. An ESD protection device  33  can protect the ESD sense device  34  and the resistor  35 . The ESD protection device  33  can also protect any other circuitry electrically connected to the pin  31 . The ESD protection device  33  is in parallel with the series combination of the ESD sense device  34  and the resistor  35  in  FIG.  3   . An ESD blocking/steering device  32  can be disposed between the pin  31  and an internal circuit (not illustrated). 
     EOS events can alternatively or additionally be sensed across certain circuit elements. Accordingly, information indicative of the functional safety of certain circuit elements can be recorded and/or reported.  FIG.  4    is a schematic diagram of a portion of an illustrative electronic device  40  configured to detect an electrostatic discharge event across a storage element according to an embodiment. In  FIG.  4   , energy associated with an ESD event can be stored as charge across a capacitor  48 . More details regarding such energy harvesting will be provided later. The ESD event detection circuit  36  of  FIG.  4    can detect an ESD event across the capacitor  48 . The ESD event detection circuit  36  of  FIG.  4    can include a counter to track the number of ESD events detected across the capacitor  48 . The ESD event detection circuit  36  of  FIG.  4    can detect an intensity of an ESD event, for example, by detecting a voltage across resistor  35  associated with the ESD event. In  FIG.  4   , the first ESD protection device  34  and the resistor  35  function similar to in  FIG.  3   . The first ESD protection device  34  can be a high impedance ESD protection device, which can be triggered by a level of an ESD event that is desired to monitor. As such, the first ESD protection device  34  need not match the other illustrated ESD protection devices  33 ,  42 , and/or  46  and/or the diode  44 . The high impedance of the first ESD protection device  34  can limit current through the resistor  35  and may conduct a relatively small percentage of current associated with an ESD event. 
     Various detection circuits  36  can be implemented to detect an EOS event. The detection circuit  36  can include any suitable circuit configured to detect an EOS. Four illustrative detection circuits  36   a ,  36   b ,  36   c , and  36   d  will be described with reference to  FIGS.  5 ,  6 ,  7 , and  8   , respectively. These detection circuits are example detection circuits that can be implemented in connection with any of the principles and advantages discussed herein, for example, with reference to  FIGS.  1 ,  3   , and/or  4 . Moreover, features of the any of the example detection circuits can be implemented in combination with any of the other example detection circuits. 
       FIG.  5    is a schematic diagram that includes a detection circuit  36   a  and an ESD protection device  34  according to an embodiment. The detection circuit  36   a  includes a comparator. As illustrated, the resistor  35  is disposed between the ESD protection device  34  and ground. A voltage generated across the resistor  35  can be compared to a reference voltage V REF . The resistance of the resistor  35  and the reference voltage can be selected such that ESD events above a threshold level trigger the comparator to indicate that an ESD event has occurred. The resistance of the resistor  35  can be selected such that the voltage across the resistor  35  provided to the comparator is at a voltage level that is unlikely to damage the comparator. The comparator can be implemented by any suitable circuitry configured to detect when the voltage across the resistor  35  exceeds a threshold that indicates that an ESD event has occurred. 
       FIG.  6    is a schematic diagram that includes a detection circuit  36   b  and an ESD protection device  34  according to another embodiment. The detection circuit  36   b  includes a plurality of comparators  36   b   1 ,  36   b   2 , and  36   b N that are each configured to compare the voltage across the resistor  35  to a different reference voltage (V REF1 , V REF2 , and V REFN , respectively). Any suitable number of comparators can be implemented. Using the plurality of comparators  36   b   1 ,  36   b   2 , and  36   b N, an intensity or level of an ESD event can be detected. The level of the ESD event can correspond to the magnitude of the highest reference voltage provided to a comparator of the plurality of comparators that detects an occurrence of an ESD event. As such, the detection circuit  36   b  can detect an occurrence of an ESD event and an intensity of the ESD event. 
       FIG.  7    is a schematic diagram that includes a detection circuit  36   c  and an ESD protection device  34  according to another embodiment. As illustrated, the detection circuit  36   c  includes a comparator  72 , a sample switch  74 , and an analog-to-digital converter (ADC)  76 . The ADC  76  can be used to determine a level of an ESD event. Like the detector circuit  36   a  of  FIG.  5   , the comparator  72  can detect an occurrence of an ESD event. Responsive to detecting an occurrence of an ESD event above a level determined by the resistance of resistor  35  and the voltage level of the reference voltage V REF , the output of the comparator  72  is toggled. This can cause the sample switch  74  to sample the voltage across the resistor  35 . The sampled voltage can be converted to a digital voltage level by the ADC  76 . The output of the ADC  76  can be indicative of a level of the ESD event. As such, the detection circuit  36   c  can provide information associated with a detected ESD event, which can indicate an occurrence of the ESD event and a level associated with the ESD event. 
       FIG.  8    is a schematic diagram that includes a detection circuit  36   d  and an ESD protection device  34  according to another embodiment. The detection circuit  36   d  is similar to the detection circuit  36   c  except a voltage across the ESD protection device  34  is used to trigger the comparator  72  and to detect a level of the ESD event. When the ESD protection device  34  is triggered, it can go into snapback mode and hold at a holding voltage with a resistance. The holding voltage can be used to detect an occurrence of an ESD event and the level of the ESD event. The ESD protection device  34  can be characterized and then characterization data can be used to determine the level of the ESD event. 
     Various memories can store information indicative of an electrical overstress event detected by the detection circuits discussed herein. Such memories can include non-volatile memories and/or volatile memories. 
     In certain embodiments, detecting an EOS can be implemented by memory elements configured to store data under certain conditions.  FIG.  9    is a schematic diagram of illustrative detection and memory circuit  90  that is configured to detect and store information associated with an ESD event according to an embodiment. The detection and memory circuit  90  can implement the functionality of the detection circuit  16  and the memory  17  of  FIG.  1 B . 
     The detection and memory circuit  90  includes fuses. Fuses are one type of non-volatile memory that can store data and/or alter the functionality of a device post manufacture. The detection and memory circuit  90  includes fuse banks  92  and  94 , a fuse bank selection circuit  96 , and a fuse bank reading circuit  98 . The fuses of one or more of the fuse banks can be configured to blow at predetermined ESD event levels. Different fuses of a selected fuse bank can blow at different ESD event levels. The fuse bank reading circuit  98  can read from one or more of the fuse banks  92  and  94  to determine whether an ESD event has occurred and a level associated with the ESD event. For instance, if any of the fuses are blown, the occurrence of an ESD event can be detected. The level associated with the ESD event can be detected based on which fuse(s) are blown. The detection and memory circuit  90  can operate even when an electronic device is not powered. The fuses can be one-time programmable such that once a fuse in a fuse bank is blown, the fuse bank selection circuit  96  can select a different fuse bank to detect an ESD event. The detection and memory circuit  90  can detect ESD events of both a positive and a negative polarity. While  FIG.  9    was described with reference to fuses for illustrative purposes, the principles and advantages discussed with this figure can be applied to other fuse elements, such as anti-fuses, and/or to other memory elements that can be selectively activated by different voltages. 
     EOS event detection can detect non catastrophic EOS events that age a device without completely damaging the device. Such functionality can monitor a circuit with slightly lower breakdown than other circuits and provide aging information about the circuit.  FIG.  10    is a schematic diagram of a portion of an electronic device  100  with an ESD event detection circuit  36  according to an embodiment. The electronic device includes a first ESD protection device  102  and second ESD protection device  104 . 
     The first ESD protection device  102  can be a diode having a relatively low breakdown voltage and a relatively small physical area and the second ESD protection device  104  can be a diode having a relatively high breakdown voltage and a relatively large physical area. These ESD protection devices are illustrated as diodes, but other suitable ESD protection devices can alternatively be implemented. The first ESD protection device  102  can trigger at a lower voltage than the second ESD protection device  104 . In an illustrative example, the first protection device  102  can trigger at about 6.5 Volts and the second ESD protection device  104  can trigger at about 7 Volts. The second ESD protection device  104  can handle more current than the first ESD protection device  102 . A resistor  35  can be in series with the first ESD protection device  102 , for example, to prevent thermal runaway and/or to provide a voltage for the detection circuit  36 . 
     With the first ESD protection device  102 , ESD events below the threshold for triggering the second ESD protection device  104  can be detected and associated data can be used to determine the age/state of “health” of a part. The ESD protection offered by the first ESD protection device  102  may not be sufficient to protect an internal circuit, but the ESD protection offered by the first ESD protection device  102  can provide a way to monitor what is happening in the second ESD protection device  104  without including a resistance, which should diminish the effectiveness of the second ESD protection device  104 , in series with the second ESD protection device  104 . 
     The detection circuit  36  can detect an ESD event using the voltage across the resistor  35 . The detection circuit  36  can blow a fuse and/or load another memory each time an ESD event is detected. After a certain number of ESD events (e.g.,  10  events) are detected, an alarm signal can be provided. For instance, the alarm signal can be toggled when all fuses can be blown and/or memory cells can overflow. The alarm signal can provide an alert to warn that a device has been aged by ESD events. 
     EOS detection circuitry can provide functional safety information at the die level and/or at a system level. At the die level, recording and monitoring EOS events can provide an indication of the functional safety of the die. Such information can be reported external to the die. An alarm signal can be provided external to the die to provide a warning about the functional safety of the die and/or to suggest that action be taken, such as replacement of the die. At the system level, detecting EOS events can provide information about functional safety at a system level. Such information can be used for predictive maintenance, for example. 
     Functional safety circuitry associated with detecting EOS events can be incorporated within a die and/or at a system level. For some expensive and/or custom integrated circuit systems where reliability and/or quality is paramount, having the capability of sensing EOS events (e.g., current surges and/or voltage surges applied from external to the system) and being able to provide information associated with the detected EOS events can be advantageous. Such information can be provided external to the integrated circuit system and/or can set an alarm within the integrated circuit system to indicate that there is a functional safety issue. Functional safety circuitry can be implemented in a variety of contexts including stacked die and/or prefabricated layers/components within a 3D vertically integrated system. 
       FIG.  11    is a diagram of stacked die  110  including a die  112  that includes functional safety circuitry according to an embodiment. The stacked die  110  can include the die  112  stacked with one or more other die  114   a ,  114   b ,  114   c . The functional safety circuitry can implement any combination of features discussed herein associated with detecting an EOS event, storing information associated with the EOS event, reporting the EOS event, providing EOS and/or ESD protection, the like, or any combination thereof. For instance, the functional safety circuitry of the die  112  can detect and record an overvoltage event or another EOS event. In some instances, the functional safety circuitry can record an intensity, a duration, a frequency, or any combination thereof of the EOS event. The functional safety circuitry can transmit the recorded information external to the stacked die  110  wirelessly by way of an antenna in an embodiment. 
       FIG.  12    is a diagram of a system in a package  120  that includes functional safety circuitry according to an embodiment. A die  112  that includes functional safety circuitry can be disposed on a circuit board  122  with other components. The die  112  and the other components can be encased within a single package. The system in a package  120  can include an over mold compound  124  that encapsulates the die  112  and other components. In this embodiment, the functional safety circuitry can provide indicators as to the effective health of the system. The indicators can be communicated externally from the system by the die  112  and/or the other components, for example, wirelessly or by being provided to an output contact of the system in a package  120 . 
       FIG.  13    is a diagram of an integrated circuit system  130  that includes functional safety circuitry according to an embodiment. The integrated circuit system  130  can be arranged to provide functionality targeted to a variety of applications. For instance, the integrated circuit system  130  can be an automotive electronics system configured for automotive applications (e.g., power steering). As another example, the integrated circuit system  130  can be a vehicular electronics system, such as an avionics electronics system configured for aircraft applications. In another example, the integrated circuit system  130  can be a healthcare electronics systems configured for healthcare monitoring (e.g., monitoring a heart rate and/or monitoring another physiological parameter) and/or for other healthcare applications. The illustrated integrated circuit system  130  includes the system in a package  120  of  FIG.  12    and other components on a system board  132 . The functional safety circuitry of the system in a package  120  can provide information indicative of potential failures with protection devices of the integrated circuit system  130  that are external to the system in a package  120 . For example, a faulty diode of the integrated circuit system  130  might fail to prevent certain undesired static currents and/or current surges. The functional safety circuitry of the system in a package  120  can monitor and record such EOS events. The functional safety circuitry can provide an external warning of such an issue. The functional safety circuitry can provide an indication of a life span of the integrated circuit system  130 . 
     Harvesting Energy from Electrical Overstress Events 
     As discussed above, aspects of this disclosure relate to harvesting energy associated with electrical overstress events, such as ESD events. The energy harvesting discussed herein can be implemented in a variety of contexts. For instance, energy harvesting can be implemented at a die or chip level. This can result in a reduction of power consumption at the die level, which can in turn reduce power consumption in a larger system. As another example, energy harvesting can be implemented at a system level, in a vertically integrated system of stacked die, or in an industrial application. A system in a package that includes energy harvesting circuitry/structures can be included in a larger system. As yet another example, energy harvesting can be implemented in a system with moving parts, such as rotating shafts, arranged to enhance harvesting of charge associated with generated static charges/EOS events. 
     Energy from EOS events can be stored by storage elements, such as capacitor(s), and the charge can be provided to the system. Accordingly, energy associated with potentially damaging EOS events can be used to power circuits. Storage elements can be activated and/or deactivated as desired. Circuitry can selectively enable and/or initiate storage element activity. For example, portions of storage elements can be discharged while other portions of storage elements can be charged. 
     The principles and advantages discussed in connection with harvesting energy associated with EOS events can be implemented in connection with any of the principles and advantages discussed with reference to detecting and recording and/or reporting EOS events. Illustrative embodiments related to harvesting energy from EOS events will now be discussed. 
     An apparatus can include an EOS steering device and a storage element configured to store charge associated with an EOS event, in which the EOS steering device can provide energy associated with an EOS event to the storage element. The EOS device can be disposed between a pin of an electronic device and the storage element. The storage element can include, for example, a capacitor. The EOS steering device can be ESD steering device and EOS event can be an ESD event. A detection circuit can be provided in combination with the storage element. The detection circuit can detect an EOS event. 
       FIG.  14    is a schematic diagram of an illustrative electronic device  140  that is configured to store charge associated with an electrical overstress event according to an embodiment. As illustrated, the electronic device  140  includes an input contact  10 , an EOS protection device  11 , an EOS steering device  142 , an internal circuit  13 , a storage element  144 , a load  148 , and an output contact  149 . The illustrated elements of the electronic device  140  can be included within a single package. The electronic device  140  can include more elements than illustrated and/or a subset of the illustrated elements. The electronic device  140  can be a die, for example. As such, in some instances, the illustrated elements of the electronic device  140  can be embodied on a single die. 
     The electronic device  140  is configured to receive an input signal at the input contact  10 , which can be an input pin as illustrated. The EOS protection device  11  is configured to provide protection from electrical overstress events. The illustrated EOS protection device  11  is configured to protect the circuitry electrically connected to the input contact  10  by diverting current associated with an EOS event to ground when a signal on the input contact  10  exceeds an EOS capability of the devices being protected, e.g., voltage breakdown. The EOS protection device  11  can protect the internal circuit  13  and the storage element  142  from electrical overstress events. In  FIG.  14   , the EOS protection device  11  is disposed between the input contact  10  and ground. The EOS protection device  11  can be disposed between the input contact  10  and any other suitable low voltage reference. The EOS protection device  11  can be an ESD protection device configured to provide ESD protection, for example. 
     The EOS steering device  142  can direct energy associated with an ESD event to the storage element  144  and to prevent charged stored by the storage element  144  from escaping. The EOS steering device can be implemented by any suitable ESD protection device, such as any of the ESD protection devices discussed with reference to  FIGS.  2 A to  2 D . The EOS steering device  142  can be disposed between the input contact  10  and the internal circuit  13 . Alternatively, an ESD isolation device can be disposed between the internal circuit  13  and the input contact  10  similar to  FIG.  1 B . It can be desirable to have an intervening circuit element between the internal circuit  13  and a pin from which energy associated with an EOS event is being harvested. 
     The storage element  144  can include one or more capacitors and/or a battery. As illustrated, the storage element  144  is in series with the EOS steering device  142 . The EOS protection device  11  is in parallel with the series combination of the EOS steering device and the storage element  144 . The load  148  can be in parallel with the storage element  144 . In some embodiments, the voltage across the storage element  144  can be regulated for providing to other circuitry. Charge from the storage element can be provided to an output contact  149  of the electronic device  140 . As such, energy harvested from an EOS event can be provided to circuitry external to the electronic device  140 . Alternatively or additionally, charge energy harvested from an EOS event can be provided to other circuitry within the electronic device, such as the internal circuit  13 , and/or to a battery of the electronic device. 
       FIG.  15    is a schematic diagram of an illustrative electronic device  150  that is configured to store charge associated with an electrical overstress event and to detect an occurrence of the electrical overstress event according to an embodiment. The electronic device  150  illustrates an example of how energy harvesting circuitry can be combined with detection circuitry configured to detect an EOS event. Another example in the context of ESD events is shown in  FIG.  4   . 
       FIG.  16    is a schematic diagram of a portion of an illustrative electronic device  160  configured to store charge associated with an electrostatic discharge event according to an embodiment. The electronic device  160  provides bipolar performance of energy harvesting of ESD events. As shown in  FIG.  16   , an ESD event can occur at pin  31 . The ESD protection device  161  can provide clamping for ESD events that exceed the capacity of the system. ESD protection devices  162  and  163  provide are arranged in parallel with diodes  164  and  165 , respectively, in  FIG.  16   . The ESD protection devices  162  and  163  can provide ESD protection for diodes  164  and  165 , respectively. In particular, these ESD protection devices can each protect a respective diode from reverse breakdown. The diodes  164  and  165  are examples of the EOS steering device  142  of  FIGS.  14  and/or  15   . The first diode  164  can steer current to charge a first capacitor  166 . The second diode  165  can steer current of an opposite polarity to charge a second capacitor  167 . Accordingly, charge associated with both positive and negative ESD events can be stored in a storage element that includes the capacitor  166  and  167 . ESD protection devices  168  and  169  can provide ESD protection for capacitors  166  and  167 , respectively. 
       FIG.  17    is a schematic diagram of a portion of an illustrative electronic device  170  configured to store charge associated with an electrostatic discharge event in a bank of storage elements according to an embodiment. Multiple ESD events can occur. Such ESD events can have different magnitudes. Having a bank of storage elements can enable charge associated with different ESD events to be efficiently stored. A plurality of switches  174   a  to  174   d  can each be arranged in series with a respective capacitor  172   a  to  172   d . In an embodiment, a selected one of the switches  174   a  to  174   d  can be on at a time. This can selectively electrically connect a selected capacitor to the diode  164 . Energy associated with an ESD event at the pin  31  can be steered by the diode  164  to capacitor of the plurality of capacitors  172   a  to  172   d  that is electrically connected to the diode  164  by way of a switch. A voltage monitoring circuit  176  can monitor the charge stored by each of the capacitors  172   a  to  172   d . The voltage monitoring circuit can detect which capacitor stores the least charge. A switch control circuit  178  can turn on a selected switch based on information from the voltage monitoring circuit  176 . Having the capacitor storing the least charge configured to capture charge associated with an ESD event can be an efficient way of capturing charge and can enable energy harvesting of as many relatively small ESD pulses as possible. 
     Various circuits can store energy associated with an EOS event. Illustrative circuits configured to store charge associated with EOS events will be described with reference to  FIGS.  18  to  22   . These circuits provide examples of circuits that can harvest energy associated with EOS events in connection with any of the principles and advantages discussed herein. Moreover, features of the any of the example energy harvesting circuits can be implemented in combination with one or more other example energy harvesting circuits. 
       FIG.  18    is a schematic diagram of a circuit  180  configured to store charge associated with an electrostatic discharge event according to an embodiment. As illustrated, the circuit  180  includes an input pin  31 , a diode  182 , a capacitor  184 , a load  186 , an output pin  188 , and a ground pin  106 . The diode  182  is an example of an EOS steering device  142  of  FIG.  14   . The capacitor  184  is an example of a storage element  144  of  FIG.  14   . When an ESD event occurs at the pin  31  and the ESD event has a positive polarity with respect to ground pin  106 , the diode  182  can be forward biased and the capacitor  184  can be charged to a voltage. The voltage across the capacitor  184  can be approximately equal to the available charge divided by the capacitance of the capacitor  184 . Once the voltage at the pin  31  drops below the voltage across the capacitor  184 , the charging phase can stop. The diode  182  can become reverse biased and the capacitor  184  can remain in a charged state. In the configuration illustrated in  FIG.  18   , the capacitor  184  can have a breakdown voltage in excess of a maximum expected voltage associated with an ESD event. The load  186  can be a resistive load, for example. The charge across capacitor  184  can be provided to other circuitry by way of output pin  188 . 
       FIG.  19    is a schematic diagram of a circuit  190  configured to store charge associated with an electrostatic discharge event according to another embodiment. The circuit  190  provides clamping and voltage regulation. The circuit  190  is like the circuit  180  of  FIG.  18    except that an ESD protection device  192  is included. The ESD protection device  192  can be arranged in parallel with the capacitor  184 . The ESD protection device  192  can function as an ESD clamp and/or protection device. The ESD protection device  192  can ensure that the voltage on a plate of the capacitor  184  opposite ground is clamped to a voltage below the breakdown of the capacitor  184 . The ESD protection device  192  can function is as a voltage regulator. When an ESD event is over, the ESD protection device  192  can shut current to ground GND until the voltage across the capacitor  184  is at approximately the breakdown voltage of the ESD protection device  192 . In a specific example, if the ESD protection device  192  has a breakdown voltage of 5 Volts, once the ESD event is over the ESD protection device  192  can shunt current to ground GND until the voltage across the capacitor  184  is approximately 5 Volts. Accordingly, the voltage stored on the capacitor  184  can be regulated to a voltage safe to be used by downstream circuits. The ESD protection device  192  can be a Zener diode as illustrated. 
       FIG.  20    is a schematic diagram of a circuit  200  configured to store charge associated with an electrostatic discharge event according to another embodiment. The circuit  200  provides clamping and voltage regulation. In  FIG.  20   , the ESD protection device  192  of  FIG.  19    is replaced by an ESD clamp circuit  202 . As illustrated, the ESD clamp cell  202  can be a stack of Zener diodes. As one example, the stack of Zener diodes can clamp the voltage across the capacitor  184  to approximately 20 Volts. The ESD clamp circuit  202  can be implemented by any suitable ESD clamp circuit such as NPN ESD device, an SCR, etc. A separate voltage regulator can be implemented, for example, by transistor  203 , diode  204 , and resistor  206 . Any other suitable voltage regulator can alternatively be implemented. Moreover, such a voltage regulator can provide any suitable regulated voltage for a particular application. 
       FIG.  21    is a schematic diagram of a circuit  210  configured to store charge associated with an electrostatic discharge event according to another embodiment.  FIG.  21    illustrates that the charge stored in connection with an ESD event can be provided to a battery  212  to recharge the battery  212 . Accordingly, energy harvested from an ESD event can be stored on a storage element, voltage can be regulated, and the battery  212  can be recharged using energy harvested from the ESD event. 
       FIG.  22    is a schematic diagram of a circuit  220  configured to store charge associated with an electrostatic discharge event according to another embodiment. An EOS energy harvester can work in a similar way to how a radio receiver works. As shown in  FIG.  22   , a basic diode detector used for AM radio can implement diode  182 . The diode  182  can receive a signal from the antenna  222  and the capacitor  184  can store charge associated with an EOS event. The diode  182  can be a crystal diode as illustrated in  FIG.  22   . Features of  FIG.  22    can be combined with a voltage regulator and the energy stored by the capacitor  184  can be provided to other circuits and/or a battery, for example, as described above. Moreover, the features of  FIG.  22    can be combined with a detection circuit configured to detect that an EOS event has occurred. Such a detection circuit can be implemented in accordance with the principles and advantages of the detection circuits discussed herein. 
     Energy harvesting circuits as discussed herein can be implemented in a variety of electronic systems. For example, such circuits can be implemented in vertically integrated systems. The energy harvesting circuitry can be implemented on a dedicated die or layer of a vertically integrated system, such as the die  112  in  FIG.  11   . Energy harvesting circuitry can be implemented at least partly on a layer in a vertically integrated system that includes prefabricated circuit elements, such as passives. Energy harvesting circuitry can be implemented at an integrated circuit level, at a system in a package level, at larger system level, or any combination thereof. When energy harvesting circuitry is implemented at a system level, die area may not be a limiting factor. Accordingly, relatively large EOS protection devices can provide higher than typical current density capabilities. Alternatively or additionally, relatively less complicated devices can be implemented at a system level, such as larger reverse biased diodes. Moreover, relatively high EOS protection can be provided at a system level and a higher level of charge may be captured than at a die level in certain applications. 
     Certain physical layouts of ESD protection devices can be implemented for high performance. The physical layouts discussed below can be implemented in connection with any of the EOS protection devices discussed herein. Example physical layouts are illustrated in  FIGS.  23 A to  23 C . 
       FIG.  23 A  provides an example of a physical layout of an ESD protection device  230 . In  FIG.  23 A , the ESD protection device is an annular structure in plan view. This can enable relatively high current handling capability. Anode  232  and cathode  234  of the ESD protection device  230  can be provided around a bond pad  236 . The weakest point of an ESD protection device can be at the end of a finger, even with increased spacings, resistances and/or curvature, as this is the location of that typically has the highest electric field. An annular ESD silicon controlled rectifier (SCR) can be used for system level ESD protection to mimic a circular device enclosing a bond pad. Such a SCR can include any combination of features described in U.S. Pat. No. 6,236,087, the entire technical disclosure of which is hereby incorporated by reference herein. 
     An annularly shaped ESD protection device in plan view can have a relatively large perimeter area and hence a relatively large cross sectional area through which the current can flow. As one example, the perimeter can be about 400 μm and the diode junction can be about 3 μm deep, thus the cross section area can be about 1200 μm 2 . Additionally, with the annular structure, metal can come out from a bond pad on four sides. This can combine to substantially minimize the resistance to an ESD zap and hence the voltage experienced by sensitive circuitry internal in the chip can be substantially minimized. Another approach that may provide an even lower resistance path to an ESD zap is a pure vertical diode where the conduction is vertically down through the silicon. In such a diode, for a 100 μm by 100 μm pad, the cross section area is 10,000 μm 2  and the metal resistance can also be relatively small as there can be a thick low resistance metal paddle on one side and a low resistance bond wire in close proximity on the other side. 
     In some instances, an ideal ESD device can be circular, as substantially the same electric field can be present along the entire a junction in such a structure. Circular ESD device layouts may not be area efficient and/or an inner anode can be smaller in junction area than an outer cathode. Circular ESD device layouts can conduct larger currents than some other common ESD layouts that consume approximately the same area. Circular ESD device layouts can conduct relatively large currents, such as currents associated with EOS events. Accordingly, such ESD device layouts can be desirable in certain applications in which an ESD device is used to harvest energy associated with an EOS event. 
       FIG.  23 B  provides an example of a physical layout of an ESD device  237 . The physical layout of the ESD device  237  is a relatively large circular shape in plan view. This can reduce the difference between junction area between the anode  232  and the cathode  234 . 
       FIG.  23 C  provides an example of a physical layout of an ESD device  238 . The ESD device  238  is implemented by a relatively dense array of smaller circular ESD devices  239 . The smaller circular ESD devices  239  can be butted against each other laterally and/or vertically. An array of smaller circular ESD devices  239  can be implemented in wearable computing devices such as smart watches, for example. 
       FIG.  24    illustrates another ESD protection device  240  where the current surge is conducted vertically through to the layer below. In the ESD protection device  240 , current can be dissipated to ground through surface  244  below N region  242 . Considering the N region  242  as a half cylinder, the ESD protection device  240  can be capable of carrying a larger current compared to an annular ESD protection structure, as the ESD protection device  240  has a larger area  244  than a corresponding annularly shaped ESD protection device. These principles can be applied when optimizing the current carrying capabilities of the structures harnessing the ESD zaps/current surges. 
     The illustrative energy harvesting circuits of  FIGS.  14  to  22    can be embodied in a variety of integrated circuit systems. Examples of such integrated circuit systems will be discussed with reference to  FIGS.  25  to  30 B . 
     In some embodiments, scaled up structures capable of harnessing an EOS event for storing charge associated with the EOS event can be provided within a vertically integrated system.  FIG.  25    provides an example of a vertically integrated system  250  with such functionality. The vertically integrated system  250  can include segregated and/or scaled up EOS protection devices so that it can handle larger surges and/or to link with a storage layer. The vertically integrated system  250  includes an ESD protection layer  252 , an insulating layer  254 , and a storage layer  256 . The ESD protection layer  252  can include ESD protection devices. In some embodiments, the ESD protection layer  252  can include a detection circuit to detect an ESD event. The ESD protection layer  252  can include coils  253  or other structures that enable signals to be sent wirelessly external to the vertically integrated system  250 . Alternatively or additionally, one or more other layers of the vertically integrated system  250  can include coils  253  or other structures that enable signals to wirelessly be sent external to the vertically integrated system  250 . The coils or other structures can send information indicative of an ESD event and/or a warning that an external system safety protection is faulty. The insulating layer  254  can serve to insulate the ESD protection layer  252  from the storage layer  256 . One or more vias  255  and/or other electrical paths can allow charge to flow from the ESD layer to the storage layer  256 . The storage layer  256  can include one any of the storage elements discussed herein, such as one or more capacitors and/or other storage elements configured to store charge associated with an ESD event. Charge stored in the storage layer  256  can be provided to other circuits. 
       FIG.  26    is a schematic diagram of a vertically integrated system  260  that includes ESD protection and energy harvesting circuitry according to an embodiment. The vertically integrated system  260  includes an ESD protection chip  261 , a storage chip  263 , and an application specific integrated circuit (ASIC)  264  having an active side  265 . Wire bonds  266  can provide electrical connections to the ESD protection chip  261  and/or the ASIC  264 . A mold compound  267  can encase the other illustrated elements within a single package. The ESD protection chip  261  can include ESD protection devices configured to provide energy associated with ESD events to storage elements of the storage chip  263 . As illustrated, the ESD protection chip  261  and the storage chip  263  are arranged in a vertical stack with the ASIC  264 . Insulating layers  262 , such as dielectric or other die attach layers, are illustrated between the different chips in  FIG.  26   . 
     By having ESD protection devices on a separate chip from the ASIC  264 , the ESD protection devices can be configured to handle ESD events having a greater magnitude than if the ESD protections devices were to be included on the ASIC  264 . The ESD protection chip  261  is electrically connected to the storage chip  263 . The storage chip  263  can be electrically connected to the ASIC  264 . The electrical connections between chips in  FIG.  26    can include wire bonds, through silicon vias, etc. The storage layer  263  can power the operation of the ASIC  264  using energy harvested from an ESD event. The integrated circuit system  260  can provide a system within a package where externally generated EOS events can be used to power the ASIC  264 . Even if a relatively small amount of power is harvested from EOS events, the cumulative reduction in total system power can be significant in time if the total system included a relatively large number (e.g., hundreds or thousands) of vertically integrated systems. 
       FIG.  27    is a schematic diagram of a vertically integrated system  270  that includes ESD protection and energy harvesting circuitry on a single chip according to an embodiment. A combined ESD protection and storage chip  272  includes circuitry capable of harnessing energy from ESD events and storage elements configured to store charge associated with the ESD events. Combined ESD protection and storage chip  272  can be stacked with an ASIC  264 . Combining the ESD protection devices and storage elements in a single die can reduce height of the vertically integrated system relative to two separate die stacked in a pyramid configuration. Combining the ESD protection devices and storage elements in a single die can reduce the length and/or resistance of a path from a surge conduction point and storage elements relative to two separately stacked die. The ASIC  264  can receive charge from storage elements of the combined ESD protection and storage chip  272 . Having the energy harvesting circuitry on a different chip than the ASIC can allow EOS protection devices, such as ESD protection devices, to be scaled up to store charge from larger EOS events, such as larger ESD events. 
       FIG.  28    illustrates a die  280  with EOS protection devices  282 , storage elements  284 , and processing circuitry  286  according to an embodiment. At a micro level, the EOS protection devices  282  can be segregated from the storage elements  284  and the processing circuitry  286  within the same die  280 . In the illustrated embodiment, the die  280  is compartmentalized to deliver a system within a chip where the storage elements  284  are electrically connected to the processing circuitry  286  as a power source. As illustrated, the die  280  is partitioned into concentric type sections. The different sections of die  280  can be combined on a single semiconductor substrate, such as a silicon substrate. Trench isolation type fab processes where selective portions can be isolated from the substrate can be used to manufacture the different sections of the die  280 . 
       FIG.  29    illustrates a die  290  with EOS protection devices  282 , storage elements  284 , and processing circuitry  286  according to an embodiment. The die  290  includes a compartmentalized arrangement where the different sections of circuitry  282 ,  284 ,  286  are separated by an isolation barrier  292  and configured in a side by side arrangement. The isolation barrier  292  can include trench isolation. The trenches can includes insulating material, such as dielectric material. In an embodiment, an isolation layer can be included around some or all of the EOS protection devices of a compartmentalized die. Alternatively or additionally, an insulating layer, such as a dielectric layer, can cover the EOS protection devices  282  and/or the storage elements  284 . 
     Energy harvesting circuitry can be implemented in mobile and/or wearable devices.  FIGS.  30 A and  30 B  illustrate an embodiment of a mobile device  300  that includes an external casing  302  having conduits  304  embedded within the external casing  302 . Mobile devices, such as mobile phones and/or other handheld devices, can include conduits  304  that are arranged for harvesting external sources of charge, such as static charge. As shown in  FIG.  30 B , electrical connections  306  can route charge from conduits  304  to energy harvesting circuitry. The energy harvesting circuitry can be embodied in a system in a package  120  as illustrated. The external casing  302  can be configured to enhance and/or optimize the delivery of charge to the energy harvesting circuitry included within the external casing  302  of the mobile device. 
     Any combination of features of the mobile device  300  can be applied to any suitable wearable device, such as a smart watch and/or a wearable healthcare monitoring device. For instance, any of the principles and advantages of the embodiments of  FIGS.  30 A and/or  30 B  can be applied to a wearable device.  FIG.  30 C  illustrates a wearable device  305  with an external casing  302  and conduits  304 . The wearable device  305  can be configured to be in contact with skin. The conduits  304  on the external casing  302  can be arranged to enhance and/or optimize the harvesting of charge from EOS events from external sources. The shape and/or arrangement of materials of the conduits  304  can enhance and/or optimize the harvesting of charge. For instance, any of the conduits  304  in any of  FIGS.  30 A to  30 C  can implement one or more features discussed in connection with  FIG.  31    and/or  FIGS.  33 A to  33 D . 
     In an embodiment, an energy harvesting system can be implemented in wearable device or another portable electronic device. The energy harvesting system can include conduits, ESD protection circuitry, a storage layer and a configuration circuit. The conduits can be arranged to efficiently channel ESD energy from an external source, such as ESD energy from contact with a person. The ESD protection circuitry configured to prevent a current spike and/or a voltage spike associated with an ESD event from damaging to other circuitry within the system. A storage layer can be configured to store the charge associated with the ESD event. The configuration circuit can configure the storage elements within the storage layer as desired to store charge associated with an ESD event. 
     The storage layer can also include ESD protection devices. The storage layer configuration circuit can control switches of the storage layer to select which storage element(s), such as capacitor(s), of the storage in which to store change associated with an ESD event. When one storage element is fully charged, the storage layer configuration circuit can adjust the state of switches such that charge associated with a subsequent ESD event is stored in another storage element. The conduits can be arranged such that the charge can only flow in one direction. The conduits can be configured to carry the maximum charge as efficiently as possible (e.g., in a circular or annular construction). The system can include a proximity sensor configured to detect a charged body. Responsive to detecting the charged body, the EDS protection circuitry can be configured and/or enabled. The system can include circuitry to recirculate charge from a storage element within the system and/or external to the system. 
       FIG.  31    illustrates examples of conductive structures of in an opening  311  of a package  312  to ESD protection devices  314  according to various embodiments. A conductive via  315  can be incorporated within the package  312  to provide signals associated with ESD events to an ESD protection device  314 . Alternatively or additionally, conductive via  316  can be incorporated within the package  312  to provide signals associated with ESD events to an ESD protection device  314 . Alternatively or additionally, a conductive connector  317  can be incorporated within the package  312  to provide signals associated with ESD events to an ESD protection device  314 . The conductive structures of  FIG.  31    are examples of electrical paths that can be enhanced and/or optimized for providing a signal associated with an ESD event for purposes of energy harvesting. 
     In some embodiments, electrical energy generation can result from rotating shafts and/or moving machine parts, for example, in industrial applications, vehicles, etc. Energy from electrical fields and/or static charge generated by rotating shafts and/or in industrial applications can generate electrical field flow and mobile carriers that can be stored by storage elements in accordance with the principles and advantages discussed herein. Example embodiments will be discussed with reference to  FIGS.  32  to  33 D . 
       FIG.  32    illustrates a system  320  that includes a rotating shaft  322  and a charge harvesting system  324  according to an embodiment. Rotation of the shaft  322  is a potential source of an electrical field and/or a static charge. The charge harvesting system  324  can include structures configured to conduct, store, and process the charge generated by rotation of the shaft  322 . The charge harvesting system  324  can be placed at or near an optimal proximity to the shaft  322  for purposes of capturing charge. The charge harvesting system  324  can be in contact with the shaft  322  or a material thereon in certain applications. The charge generated and stored within the charge harvesting system  324  can then be re-circulated and/or used for another function and/or to power components within the charge harvesting system  324 . 
     The charge harvesting system  324  can harvest energy from parts, such as shafts, that move to perform other functions. Accordingly, energy that would otherwise be lost in a system can be captured by the charge harvesting system  324 . Existing equipment and/or machinery can be retro-fitted with a charge harvesting system  324  to capture charge and re-circulate the captured charge to the system. Charge harvesting systems  324  can be incorporated into smart vehicles and/or electric vehicles such that, in certain circumstances (e.g., moving parts due to kinetic energy and/or physical momentum associated with going down a hill), charge can be generated and then stored and re-circulated within the vehicle. 
     The amount of charge generated by moving and/or rotating machinery can be enhanced and/or optimized by material selection. Materials used to construct moving parts can be selected along with other materials placed in close proximity to improve the intensity of the generated electrical field and/or amount of generated charge. 
       FIG.  33 A  illustrates a rotating shaft  322  having a layer of material  332  for enhancing an ESD field and/or charge generated by the rotating shaft and a charge harvesting system  324  having a layer of material  334  for enhancing an ESD field and/or charge generated. Surfaces of material  332  and the charge harvesting system  324  can be in physical contact with each other for an ESD field from the rotating shaft to be discharged to the charge harvesting system. Alternatively, the material  332  and the charge harvesting system  324  can be in close proximity to each other and a large enough charge to enable air-gap arcing can cause discharge from the rotating shaft to the charge harvesting system. Materials  332  and  334  can be selected and/or shaped to enhance and/or optimize charge generated by the shaft  332  and stored by the charge harvesting system  324 . As shown in  FIG.  33 A , the rotating shaft  322  can have the layer of material  332  disposed around the circumference of the shaft  322 . For instance, the layer of material  332  can be a ring and/or collar. The material  332  can be selected such that it maximizes the field generated when the shaft  322  is rotated in close proximity to the charge harvesting system  324 , which can include another material layer  334  that can be exposed to the material  332 . The charge harvesting system  324  can harvest ESD energy and can conduct the generated charge to the layers within the system. The charge can be stored in any of the storage elements discussed herein. The stored charge can then be circulated and/or applied to power up other operations within the charge harvesting system  324  and/or external to the charge harvesting system  324 . 
       FIG.  33 B  illustrates that the layer of material  332 ′ incorporated on the rotating shaft  322  can have a non-uniform width in certain embodiments. The width of the layer of material  332 ′ can have a varying width as illustrated. The change in the width of the layer of material  332 ′ can produce a discernible shift in the generated electric field between the layer of material  332 ′ and the layer of material  334 , which can be detected by the energy harvesting system  324 . This measured change in the electrical field can be used in a number of ways, including to measure the revolutions per unit time of the shaft  322  based on the discernible change in electric field between the layers of material  332 ′ and  334  as the shaft  322  rotates and/or to intentionally use the changing and/or intermittent peak nature of the electric field to electrically manipulate/move/operate the layers within the charge harvesting system  324  at defined periodic intervals. 
       FIG.  33 C  illustrates a selected surface topography of the layer of material  334 ′ of the energy harvesting system  324  according to an embodiment. The topography of the layer of material  334 ′ can be modified relative to a planar layer to increase the surface area of the material exposed to the rotating shaft  322 , for example, as illustrated. Accordingly, the electric field generated can be increased. 
       FIG.  33 D  illustrates a surface finish  336  on the layer of material  334 ′ of the energy harvesting system  324  according to an embodiment. Recesses in the layer of material  334 ′ can be filled with a surface finish material  336  to enhance and/or optimize charge associated with ESD events. The surface finish material  336  can be selected to optimize charge and/or electric field generated relative to the layer of material  332 ′. Accordingly the interaction and/or shape of the materials of the layers  332 ′ and/or  334 ′ and/or the surface finish  336  can optimize the electric field generated by the rotating shaft  322 . 
     Various patterns and/or arrangements of the materials  332  and/or  334  can be implemented to enhance and/or optimize properties of electric fields and/or other electrical effects generated by the rotating shaft  322 . Example patterns include concentric shapes, such as concentric circles or concentric squares, pyramidal stacked layers, rows of material with another material disposed over the rows of material, the like, or any combination thereof. 
     When two different materials are pressed or rubbed together, the surface of one material can generally capture some electrons from the surface of the other material. The material that captures electrons can have a stronger affinity for negative charge of the two materials, and that surface can be negatively charged after the materials are separated. Of course, the other material should have an equal amount of positive charge. If various insulating materials are pressed or rubbed together and then the amount and polarity of the charge on each surface is separately measured, a reproducible pattern can emerge. For insulators, Table 1 below can be used to predict which will become positive versus negative and how strong the effect can be. Such materials can be selected for purposes of generating charge in the embodiments of  FIGS.  33 A to  33 D . Electroactive polymers are some other examples of materials that can be used in generating charge. Polarization can be inducted by electric field and polarization can modify the electric field. Accordingly, polarization can modify an intensity of an electric field. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Typical Material Correction Factors 
               
            
           
           
               
               
               
               
            
               
                   
                 Material 
                 Correction Factor 
                 Type of Metal 
               
               
                   
                   
               
               
                   
                 Steel (Fe360) 
                 1.0 
                 Ferrous 
               
               
                   
                 Stainless Steel 
                 0.6 . . . 1.0 
                 Non-Ferrous 
               
               
                   
                 Aluminum 
                 0.30 . . . 0.45 
                 Non-Ferrous 
               
               
                   
                 Brass 
                 0.35 . . . 0.50 
                 Non-Ferrous 
               
               
                   
                 Copper 
                 0.25 . . . 0.45 
                 Non-Ferrous 
               
               
                   
                   
               
            
           
         
       
     
     Any of the principles and advantages described in connection with materials and/or patterns/arrangements of materials to enhance and/or maximize electric fields/generated charge can also be applied to monitor system utilization. For example, where the change in electric field generated by a material and/or a pattern/arrangement of materials can be proportional to a state, such as a particular state of operation of the system, information indicative of the state can be communicated remotely from the system. Such information can be used in monitoring the system. 
     The principles and advantages discussed herein with reference to harvesting energy from EOS events can be applied to a variety of contexts in which an object carrying charge approaches another object. The object carrying charge can provide the EOS. For example,  FIG.  33 E  is a block diagram of a context in which energy harvesting can be implemented according to an embodiment. In  FIG.  33 E , a vehicle  335  can approach a docking station  336 . The docking station  336  can include EOS protection circuits and circuits to be protected. The docking station  336  can include energy harvesting circuitry and/or EOS detection and recording circuitry. The charge harvested by the docking station  336  can be used to power circuits of the docking station. In an embodiment, static charge generated by the vehicle  335  can be used to charge an electric vehicle, for instance, when the docking station  336  can perform a charging function. The vehicle  335  can include structures/materials  337  that can be configured to enhance and/or optimize a generated field in combination with another structure/material  338  associated with the docking station  338 . The structures  337  and/or  338  can implement one or more features discussed above, for example, in connection with a rotating shaft. The vehicle  335  can include functional safety circuitry in certain implementations. 
     Responsive to detecting the vehicle  335  approaching the docking station  336 , the energy harvesting circuitry and/or EOS detection and recording circuitry can be enabled and/or pre-conditioned. A proximity sensor, such as discussed below, can detect that the vehicle  335  (e.g., a car, a truck, a subway train, a train, a forklift, etc.) is approaching the docking station  336 . 
     Smart storage aspects of harvesting changed associated with EOS events, such as switching on and off different capacitors, enabling protective circuitry, the act of sensing the presence of something, can be applied in a variety of contexts. For example, in the case of a smart/electric vehicle, smart storage circuitry, such as the storage circuitry of the electronic device  170  of  FIG.  17   , can be incorporated within a system whereby the charge/storage levels are recorded and/or transmitted wirelessly to implement a variety of functionalities. For instance, a fleet of “smart” forklifts/vehicles could be managed/monitored, for example, when stored charge of a specific vehicle gets to a certain level, the system can flags this and initiate a plans for the specific vehicle to recharge. As another example, within a “smart” vehicle when a storage level gets to a certain level this enables a “smarter” use of system power, such as temporarily turning off non-essential functionality. As another example, before/during docking a level of power within the storage system can be remotely transmitted to the docking station and this can enables more effective charging/energy management at the docking station. In another example, energy harvesting circuitry can harness and store the charge carried by a vehicle for use by the vehicle. In one other example, a docking station can harvest static charge generated by a vehicle and used the harvested charge to perform a charging function. 
     Energy harvesting circuitry and/or storage elements can be physically implemented in a variety of ways.  FIGS.  36  to  41    provide illustrative physical embodiments of energy harvesting circuitry configured to store energy associated with EOS events in storage elements. Any of these embodiments can include EOS event detection circuitry. In these embodiments, exposed surfaces of EOS can, for example, include circular conducting structures or arrays of such circular conducting structures. Any of the principles and advantages discussed with reference to energy harvesting and storage layers, such as circuits, materials, layers, etc., can be implemented in connection with any of  FIGS.  36  to  41   . 
     In  FIG.  36   , electronic device  360  includes EOS protection layers  252  on opposing sides. The EOS protection layers  252  in this electronic device can harvest change on opposing sides of the electronic device. The EOS protection layers  252  can include EOS devices and/or other circuitry for generating charge associated with EOS events. Each of the EOS protection layers  252  can be connected to the storage layer  256 , which includes storage elements to store the harvested charge. Insulating material can be included between each of the EOS protection layers  252  and the storage layer  256 . In another embodiment, separate storage layers can be included for each EOS protection layer  252 . As illustrated, the electronic device  360  also includes an ASIC  264 . 
     In  FIG.  37   , the electronic device  370  includes side by side EOS protection layers  252 . As illustrated, each of these EOS protection layers  252  are in electrical communication with a respective storage layer  256 . The illustrated electronic device  370  includes separate vertical stacks of an EOS protection layer  252 , a storage layer  256 , and an ASIC  264 . 
     The electronic device  380  of  FIG.  38    includes an opening  382  through which EOS devices of the EOS layer  252  are exposed. Such a device can be used in a variety of different EOS event detection and/or EOS event harvesting applications. 
     The electronic device  390  of  FIG.  39    includes an opening  392  through which EOS devices of the EOS layer  252  are exposed at the bottom of a recess. Such a device can be used in a variety of different EOS event detection and/or EOS event harvesting applications. 
     The electronic device  400  of  FIG.  40    includes EOS devices of EOS layers  252  within an opening between two sides of an embedded structure. Such a device can be used in a variety of different EOS event detection and/or EOS event harvesting applications. 
     The electronic device  410  of  FIG.  41    includes EOS devices of EOS layers  252  within an opening/recess of an embedded structure. Such a device can be used in a variety of different EOS event detection and/or EOS event harvesting applications. 
     Proximity of an Electric Field and EOS Protection and/or Energy Harvesting Configuration 
     As discussed above, aspects of this disclosure relate to detecting proximity of an electrical field and configuring circuitry for EOS protection and/or harvesting energy from an EOS event responsive to detecting proximity. Proximity sensing information can be used to configure EOS protection circuitry and/or energy harvesting circuitry configured to store energy associated with EOS events. Proximity sensing information can indicate proximity of an object in one, two, or three dimensions. The principles and advantages associated with using proximity sensing information to configure devices can be applied in connection with any of the other embodiments discussed herein. Illustrative embodiments related to proximity sensing will now be discussed. 
       FIG.  34    is a schematic block diagram of an illustrative electronic device that can configure EOS protection using proximity sensing information according to an embodiment. As illustrated, the electronic device  340  includes an input contact  10 , an EOS protection device  11 , a proximity sensor  342 , and an EOS configuration circuit  344 . The proximity sensor  342  can be any suitable sensor configured to sense proximity of an object to the electronic device  340 . For instance, the proximity sensor  342  can be a capacitive sensor or a magnetic sensor in certain implementations. The proximity sensor  342  can provide proximity information to the EOS configuration circuit  344 . The EOS configuration circuit  344  can enable EOS protection. The EOS configuration circuit  344  can configure the EOS protection device  11  based on the proximity information. Accordingly, the EOS protection device can be configured prior to an EOS event resulting from an object in proximity to the electronic device. The EOS configuration circuit  344  can, for example, provide active voltage clamping of the EOS protection device  11  and/or provide current to an actively controlled protection circuit, such as an actively controlled SCR. 
     According to certain embodiments, the EOS protection device  11  can be an ESD protection device. The EOS configuration circuitry  344  can pre-trigger and/or prime the ESD protection device to trigger responsive to the proximity information indicating that an ESD event is likely imminent. When there is a race condition between the ESD protection and the internal circuits to be protected, such pre-triggering and/or priming can ensure proper ESD protection of the internal circuits. Pre-triggering an ESD protection device can provide more robust ESD protection for fast ESD events, such as ESD events on the order of nanoseconds or less. 
       FIG.  35    is a schematic block diagram of an illustrative electronic device that can configure a storage element arranged to store energy associated with an EOS event using proximity sensing information according to an embodiment. As illustrated, the electronic device  350  includes an input contact  10 , an EOS protection device  11 , an EOS steering device  142 , a storage element  144 , a load  148 , an output contact  149 , a proximity sensor  342 , and a storage element configuration circuit  354 . In  FIG.  35   , the proximity sensor  342  can provide proximity information to the storage element circuit  344 . The storage element configuration circuit  354  can configure the storage element  144  based on the proximity information. Accordingly, the storage element  144  can be configured prior to an EOS event resulting from an object in proximity to the electronic device. Based on the proximity information, particular capacitor(s) and/or other storage structure(s) of the storage element  144  can be switched in to capture charge associated with the EOS event. The particular capacitor(s) and/or other storage structure(s) that are switched in based on capacity to capture energy associated with an EOS event. The particular capacitor(s) and/or other storage structure(s) can later be switched out after the charge associated with the EOS event is captured. 
     CONCLUSION 
     The principles and advantages described herein can be implemented in various apparatuses. Examples of such apparatuses can include, but are not limited to, consumer electronic products, parts of the consumer electronic products, electronic test equipment, etc. Examples of parts of consumer electronic products can include clocking circuits, analog-to-digital converts, amplifiers, rectifiers, programmable filters, attenuators, variable frequency circuits, etc. Examples of the electronic devices can also include memory chips, memory modules, circuits of optical networks or other communication networks, and disk driver circuits. Consumer electronic products can include, but are not limited to, wireless devices, a mobile phone (for example, a smart phone), cellular base stations, a telephone, a television, a computer monitor, a computer, a hand-held computer, a tablet computer, a laptop computer, a personal digital assistant (PDA), a microwave, a refrigerator, a stereo system, a cassette recorder or player, a DVD player, a CD player, a digital video recorder (DVR), a VCR, an MP3 player, a radio, a camcorder, a camera, a digital camera, a portable memory chip, a washer, a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, a wrist watch, a smart watch, a clock, a wearable health monitoring device, etc. Further, apparatuses can include unfinished products. 
     Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” “include,” “including,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The words “coupled” or connected”, as generally used herein, refer to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number, respectively. The words “or” in reference to a list of two or more items, is intended to cover all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. All numerical values provided herein are intended to include similar values within a measurement error. 
     Moreover, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. 
     The teachings of the inventions provided herein can be applied to other systems, not necessarily the systems described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments. The acts of the methods discussed herein can be performed in any order as appropriate. Moreover, the acts of the methods discussed herein can be performed serially or in parallel, as appropriate. 
     While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure. Accordingly, the scope of the present inventions is defined by reference to the claims.