PATENT DOCUMENT

Publication Number: US-9285278-B2
Application Number: US-201313891030-A
Country: US
Kind Code: B2

Title: System and methods for thermal control using sensors on die

Abstract:
A portable electronic device including a temperature sensor embedded in a die is provided. To process temperature measurements the portable electronic device includes a processor circuit coupled to the temperature sensor, the processor circuit configured to read a measurement from the temperature sensor when an integrated circuit in the die is inactive. Furthermore, a memory circuit coupled to the processor circuit and the temperature sensor stores a temperature gradient provided by the temperature sensor. A Printed Circuit Board for use in a portable electronic device as above is also provided. A method for performing thermal control in a portable electronic device as above is also provided.

Claims:
What is claimed is: 
     
       1. A Printed Circuit Board (PCB) in communication with a processor circuit and configured to determine a representative temperature of the PCB, the PCB comprising:
 a first temperature sensor embedded within a first integrated circuit (IC) directly measuring a first temperature of the first integrated circuit (IC); 
 a second temperature sensor embedded within a second integrated circuit (IC) directly measuring a second temperature of the second IC; 
 a component; and 
 wherein the processor circuit is configured to:
 receive the first temperature and the second temperature, 
 run a simulation program stored on a memory circuit to establish a temperature gradient, based upon the first temperature and the second temperature, across the PCB, and 
 perform a remedial action to the component based upon the temperature gradient. 
 
 
     
     
       2. The PCB as recited in  claim 1 , wherein the remedial action comprises deactivating the component to define a sleep mode of the component. 
     
     
       3. The PCB as recited in  claim 1 , wherein the processor circuit, the memory circuit, first IC, and the second IC are disposed on the PCB. 
     
     
       4. The PCB as recited in  claim 3 , further comprising:
 a third temperature sensor embedded within a third integrated circuit (IC) directly measuring a third temperature of the third IC disposed on the PCB, wherein the processor circuit is configured to run the simulation program stored on the memory circuit to establish the temperature gradient based upon the first temperature, the second temperature, and the third temperature. 
 
     
     
       5. The PCB as recited in  claim 4 , wherein at least one of the first IC, the second IC, or the third IC comprises a power amplifier used for a radio frequency antenna. 
     
     
       6. The PCB as recited in  claim 5 , wherein when the processor circuit runs the simulation program to establish the temperature gradient, the processor circuit does not use a temperature from one or more inactive integrated circuits. 
     
     
       7. The PCB as recited in  claim 6 , wherein the component comprises a battery. 
     
     
       8. A portable electronic device configured to perform a remedial action in response to a thermal flux within the portable electronic device, the portable electronic device comprising:
 a printed circuit board (PCB); 
 a temperature sensor embedded within an IC disposed on the PCB and that directly measures a temperature of the first IC; 
 a processor circuit that receives multiple temperature readings of the PCB from the temperature sensor embedded within the IC to establish a simulated temperature gradient across the PCB based upon the multiple temperature readings; 
 a memory circuit that sends to the processor circuit a simulation program to establish the simulated temperature gradient; and 
 a component disposed on the PCB, the component receiving the remedial action based upon the simulated temperature gradient. 
 
     
     
       9. The portable electronic device as recited in  claim 8 , further comprising:
 a second temperature sensor embedded in a second IC disposed on the PCB; 
 a third temperature sensor embedded in a third IC disposed on the PCB; and 
 wherein the multiple temperature readings are determined by the temperature sensor, the second temperature sensor, and the third temperature sensor. 
 
     
     
       10. The portable electronic device as recited in  claim 8 , wherein the processor circuit processes a statistical operation of the multiple temperature readings to determine the simulated temperature gradient. 
     
     
       11. The portable electronic device as recited in  claim 10 , wherein the statistical operation comprises an average of the multiple temperature readings only from a first temperature sensor and a third temperature sensor. 
     
     
       12. The portable electronic device as recited in  claim 11 , wherein the first temperature sensor is closer to the component than the second temperature sensor and the third temperature sensor.

Description:
FIELD OF THE DESCRIBED EMBODIMENTS 
     The described embodiments relate generally to methods, devices, and systems for thermal control in portable electronic devices. More particularly, embodiments disclosed herein relate to thermal control in portable electronic devices using sensors formed in a circuit die included in a Printed Circuit Board (PCB). 
     BACKGROUND 
     In the field of portable electronic devices, it is important to control device temperature on a real time basis. For that purpose, it is customary to include a thermistor or some other temperature sensor in a sensitive area of a printed circuit board (PCB). Continuous monitoring of the temperature sensor thus provides an accurate value of the PCB temperature in different points of the circuit. The downside of such approaches is the excess space (‘real estate’) used by the temperature sensor in the PCB layout. Concern for the usage and optimization of real estate in PCB circuitry for portable electronic devices is a major drive for design innovation and optimization. On the other hand, as portable electronic devices broaden their range of applicability and capabilities, there is an increased redundancy of circuitry in the PCB layout of such devices. As a result, for a standard portable electronic device there is typically a number of idle circuits in the PCB layout. 
     Therefore, what is desired is a method and a system for real time temperature monitoring in a portable electronic device without increasing a demand for real state in the PCB layout. What is also desired is an efficient use of circuitry already existing in a PCB layout for real time temperature monitoring. 
     SUMMARY OF THE DESCRIBED EMBODIMENTS 
     In a first embodiment, a portable electronic device is provided, the portable electronic device including a printed circuit board (PCB) and a die including an integrated circuit (IC), the die embedded in the PCB. The portable electronic device may further include a temperature sensor embedded in the die. To process temperature measurements the portable electronic device includes a processor circuit coupled to the temperature sensor, the processor circuit configured to read a measurement from the temperature sensor. Furthermore, a memory circuit coupled to the processor circuit and the temperature sensor stores a temperature gradient provided by the temperature sensor. 
     In a second embodiment, a Printed Circuit Board (PCB) for use in a portable electronic device is provided. The PCB includes a die having an integrated circuit (IC) and embedded in the PCB. A temperature sensor included in the die is configured to collect temperature measurements, and a processor circuit coupled to the temperature sensor reads a measurement from the temperature sensor and calculates a temperature gradient. A memory circuit coupled to the processor circuit and the temperature sensor stores a temperature gradient provided by the temperature sensor. 
     In a third embodiment, a method for performing thermal control in a portable electronic device, the method includes simulating a temperature gradient of an area of interest in a Printed Circuit Board (PCB); selecting a temperature sensor; collecting the temperature sensor reading; obtaining a measurement of the temperature gradient of the area of interest; and performing a remedial action in the area of interest. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The described embodiments may be better understood by reference to the following description and the accompanying drawings. Additionally, advantages of the described embodiments may be better understood by reference to the following description and accompanying drawings. These drawings do not limit any changes in form and detail that may be made to the described embodiments. Any such changes do not depart from the spirit and scope of the described embodiments. 
         FIG. 1  illustrates a printed circuit board (PCB) configured for thermal control of a portable electronic device, according to some embodiments. 
         FIG. 2  illustrates a PCB configured for thermal control of a portable electronic device, according to some embodiments. 
         FIG. 3  illustrates a flow chart in a method for thermal control of a portable electronic device, according to some embodiments. 
         FIG. 4  illustrates a flow chart in a method for thermal control of a portable electronic device, according to some embodiments. 
         FIG. 5  illustrates a flow chart in a method for thermal control of a portable electronic device, according to some embodiments. 
         FIG. 6  illustrates a flow chart in a method for thermal control of a portable electronic device, according to some embodiments. 
     
    
    
     In the figures, elements referred to with the same or similar reference numerals include the same or similar structure, use, or procedure, as described in the first instance of occurrence of the reference numeral. 
     DETAILED DESCRIPTION OF SELECTED EMBODIMENTS 
     Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
     Typical configurations for thermal control of a portable electronic device may use one thermistor circuit embedded in the printed circuit board (PCB). The signal from such thermistor circuit provides an indication of the overall temperature of the electronic device and is used as part of the thermal control around the unit. To provide a more accurate temperature value, it is desirable that the temperature sensor be placed at a distance from an thermal component. Indeed, thermal components may intermittently draw large amounts of power, heating up and cooling down through cycles that may not be indicative of an overall device temperature. Some of these thermal components may include power amplifiers (PA) for radio-frequency (RF) antennas. On the other hand, there may be natural hot spots in an electronic device where it is desirable to have a temperature sensor nearby. Such a natural hot spot may be a battery in a portable electronic device, or a radio-frequency (RF) processing circuit. 
     Temperature sensors embedded in the PCB (‘board sensors’) and separated from active dies typically have a long and steady thermal transient response. The thermal signal provided by board sensors is not subject to large transient cycles, therefore is useful for thermal control at a device scale. However, board sensors typically take real estate on the PCB layout. For example, a board sensor may use a specifically designed area in the mother board of a device. According to embodiments disclosed herein, it is desirable to avoid usage of real state in the PCB for maintenance and control operations, which is desirable in the context of device miniaturization. To increase availability of real estate in the PCB, embodiments disclosed herein include temperature sensors embedded in functional dies in the PCB, thus saving real estate on the mother board of the device. A temperature sensor (‘die sensor’) may be very dynamic and do not offer a very stable thermal signal to be used for thermal control. 
       FIG. 1  illustrates a printed circuit board (PCB)  100  configured for thermal control of a portable electronic device, according to some embodiments. PCB  100  may include dies  110 - 1 ,  110 - 2 , and  110 - 3 , each corresponding to an integrated circuit (IC) having a specific application (hereinafter collectively referred to as dies  110 ). Accordingly, dies  110  may correspond to application specific ICs (ASICs). In some embodiments, dies  110  may include RF Power Amplifiers (PAs). For example, multiple RF Pas may be used in portable electronic devices to handle multiple RF antennas. The number of dies  110  included in PCB  100  is not limiting of embodiments consistent with the present disclosure. While  FIG. 1  shows three dies  110 - 1 ,  110 - 2 , and  110 - 3 , any number of dies may be included in PCB  100 , according to embodiments consistent with the present disclosure. Also shown in  FIG. 1  is temperature sensor  101 - 1  included in die  110 - 1 , temperature sensor  101 - 2  included in die  110 - 2 , and temperature sensor  101 - 3  included in die  110 - 3 . Hereinafter, temperature sensors  101 - 1 ,  101 - 2 , and  101 - 3  will be collectively referred to as temperature sensors  101 . 
     Temperature sensors  101  may be any type of electronic circuit configured to measure temperature, such as a thermistor. In some embodiments, temperature sensor  101  may include a thermocouple, or any other temperature sensing circuit. FIG.  1  also includes a processor circuit  111  and a memory circuit  112  within the layout of PCB  100 . Processor circuit  111  and memory circuit  112  are coupled to one another, so that processor circuit  111  executes commands from code stored in memory circuit  112 . Processor circuit  111  may also read data from and write data to, memory circuit  112 . Processor circuit  111  and memory circuit  112  are coupled to each of temperature sensors  101 . Processor circuit  111  may receive temperature values from at least one of temperature sensors  101 . Furthermore, processor circuit  111  may use the temperature from temperature sensors  101  as input values for a simulation program stored in memory circuit  112 . Thus, processor circuit  111  may compute a temperature gradient chart, or temperature map, of PCB layout  100 . 
     In embodiments consistent with the present disclosure, it is desirable to have an accurate estimate of the thermal performance of the electronic device operated by circuitry in PCB  100 . Accordingly, a temperature value associated to the PCB substrate may better represent the thermal flux within the portable device. During operation of the electronic device, several of the dies  110  may become active at different time intervals. During an active period, a certain die  110  may draw a large amount of power, thus dissipating a large amount of heat. The die corresponding to the active power amplifier may thus be heated to an exceedingly high temperature, not representative of the overall temperature in the rest of PCB  100 . A measurement provided by a temperature sensor in such circuit may be unrealistically high, for the purposes of estimating heat flux within the portable electronic device. Thus, in some embodiments it may be desirable to use values provided by temperature sensors included in dies  110  including inactive ICs, or that typically draw a moderate to low amount of power during operation. 
     In some embodiments, dies  110  correspond to power amplifiers for RF antennas. For example, in a typical portable electronic device each one of dies  110 - 1 ,  110 - 2 , and  110 - 3  may be a power amplifier for an RF antenna operating in a given frequency band. In that regard, during RF communication only one of dies  110  may be used regularly. In fact, in some embodiments a number of dies  110  may remain idle for most of the usable period of the portable electronic device. For example, in some embodiments the device may be regularly operated in a first geographical area where RF radiation in a first bandwidth is simply unavailable. A first power amplifier die in PCB  100  tuned for the first bandwidth may remain idle for as long as the device is operated in the first geographical area. For clarity, the first power amplifier may be referred to as “OFF Band” power amplifier. A temperature sensor included in the “OFF Band” may be used to provide temperature data. 
     Some embodiments such as illustrated in  FIG. 1  may use temperature provided from multiple temperature sensors  101  in order to obtain a more accurate temperature gradient. For example, in some embodiments the minimum temperature value provided at any given point in time by multiple temperature sensors  101  may be used. As dies  110  may be turned ‘on’ and ‘off’ intermittently, a minimum value from a plurality of temperature sensors may be sufficiently stable. In some embodiments the average of multiple values provided by temperature sensors  101  may be used for thermal control. Further according to some embodiments, a statistical operation may be performed to the measurement values provided by multiple temperature sensors  101  across PCB  100 . For example, in some embodiments the lowest measurement value may be discarded from a measurement set. Or the highest measurement value may be discarded from a measurement set. Or both the lowest and the highest values may be discarded from a measurement set. In the above embodiments, processor  111  may process and perform statistical operations with temperature data provided by temperature sensors  101 . Thus, temperature sensors  101  according to the above embodiments may provide a steady thermal signal response. Furthermore, when a radio system in a portable electronic device as disclosed herein alternates from one PA to another, a temperature sensor in a third, idle PA may provide an accurate thermal response through the dynamic transition. For example, die  110 - 1  may be a PA operating in a first RF band and die  110 - 3  may be a PA operating in a third RF band. During operation of the portable electronic device, the device may alternate activation between die  110 - 1  and die  110 - 3 , while PA die  110 - 2  remains idle. In such configuration, processor  111  may determine that a temperature reading from temperature sensor  101 - 2  in idle PA die  110 - 2  is a desirable choice. 
       FIG. 2  illustrates a PCB  200  configured for thermal control of a portable electronic device, according to some embodiments. PCB  200  includes dies  110 , temperature sensors  101 , processor circuit  111 , and memory circuit  112 , described in detail above (cf.  FIG. 1 ). PCB  200  in  FIG. 2  also includes a thermal component  220  that may be a ‘hot spot’ in PCB  200 . For example, thermal component  220  may be a battery in a handheld electronic device. In that regard, thermal component  220  may be a constant heat source due to extended periods of operation. A constant heat source may be an element in PCB  200  that is at a higher temperature than its surroundings for an extended period of time, relative to the period of time during which the electronic device is operating. Thermal component  220  may be coupled to PCB  200 , but not inside PCB  200 , nor embedded in PCB  200 . Thus, to have an accurate description of a thermal gradient distribution across PCB  200 , it may be desirable to place a temperature sensor  101  in a die  110  proximal to thermal component  220 . Further according to some embodiments thermal component  220  may be a heat sink that remains at a lower temperature relative to other components in PCB  200 . For example, thermal component  220  may be a glass forming part of a window of the portable electronic device. 
     In embodiments consistent with the present disclosure, processor circuit  111  may determine that die  110 - 3  is closest to thermal component  220 . And processor circuit  111  may determine that die  110 - 1  is farthest to thermal component  220 . In such configuration, processor circuit  111  may select measurements from temperature sensors  101 - 1  and  101 - 3 . Moreover, in some embodiments processor circuit  111  may average the measurements from temperature sensors  101 - 1  and  101 - 3 . Further according to some embodiments, processor circuit  111  may select the lowest value from the measurements provided by temperature sensors  101 - 1  and  101 - 3 . 
       FIG. 3  illustrates a flow chart in a method  300  for thermal control of a portable electronic device, according to some embodiments. A portable electronic device in method  300  may include a PCB layout having dies, each die including a temperature sensor (e.g., PCB  100 , dies  110 , and temperature sensors  101 , cf.  FIG. 1 ). Furthermore, the PCB layout in method  300  may include a processor circuit and a memory circuit (e.g., processor circuit  111  and memory circuit  112 , cf.  FIG. 1 ). Accordingly, steps in method  300  may be partially or completely performed by the processor circuit executing commands, storing data, and using data stored in the memory circuit. 
     Step  310  includes simulating a temperature gradient of an area of interest in the PCB based on pre-selected temperature sensor values. Step  310  may include associating each of a plurality of points in the PCB layout with a temperature value. Accordingly, step  310  may be performed using a computer aided design (CAD) program, using a set of pre-existing measured data, or a combination of both. The CAD program may be stored in the memory circuit and executed by the processor circuit in the PCB layout. In some embodiments, the CAD program may be stored in a memory circuit and executed by a processor circuit not included in the PCB layout. In such embodiments, the thermal gradient model resulting from step  310  may be stored in the memory circuit in the PCB layout 
     Step  320  includes selecting a temperature sensor for a temperature reading. Accordingly, step  320  may include selecting a temperature sensor in an idle die of the PCB layout. Furthermore, step  320  may include selecting a temperature sensor from a plurality of temperature sensors. As discussed above in relation to  FIGS. 1 and 2 , step  320  may include selecting a temperature sensor located proximal to an thermal component in the PCB layout. For example, step  320  may include selecting a temperature sensor located proximal to a heat source in the PCB layout, or in the electronic device. In some embodiments step  320  may include a temperature sensor located distal from an a thermal component. The thermal component in step  320  may be a heat sink, in some embodiments. 
     Step  330  includes collecting temperature sensor readings from the selected temperature sensor. Step  330  may include storing at least a sensor reading in the memory circuit. Step  340  includes obtaining a temperature gradient of the area of interest. Accordingly, step  340  may include using the temperature sensor reading in the temperature gradient model obtained in step  310 . For example, the temperature sensor reading may be a boundary value in a temperature gradient model created in step  310 . Thus, step  340  may include creating a thermal gradient or a thermal map from the boundary value provided to the thermal gradient model. 
     Step  350  includes performing a remedial action in the area of interest based on the temperature gradient obtained. In some embodiments, step  350  may include turning ‘off’ an integrated Circuit (IC) embedded in the PCB. Further according to some embodiments, step  350  may include performing a remedial action in the area of interest comprises setting an IC in ‘sleep’ mode. 
       FIG. 4  illustrates a flow chart in a method  400  for thermal control of a portable electronic device, according to some embodiments. A portable electronic device in method  400  may include a PCB layout having dies, each die including a temperature sensor (e.g., PCB  100 , dies  110 , and temperature sensors  101 , cf.  FIG. 1 ). Furthermore, the PCB layout in method  400  may include a processor circuit and a memory circuit (e.g., processor circuit  111  and memory circuit  112 , cf.  FIG. 1 ). Accordingly, steps in method  300  may be partially or completely performed by the processor circuit executing commands, storing data, and using data stored in the memory circuit. In some embodiments, steps in method  400  may be performed in the context of step  320  in method  300 , described in detail above (cf.  FIG. 3 ). 
     Step  410  includes polling circuits in the PCB layout. Accordingly, step  410  may include querying for each IC in the PCB layout whether the circuit is active or idle. When the circuit is active, step  410  may skip the temperature sensor included in the die for the circuit. Thus, data measured by temperature sensors located in dies with active ICs may not be collected. Step  420  may include forming a measurement set having temperature sensors from idle circuits, as determined in step  410 . Accordingly, step  420  may include forming a measurement set including one element, e.g., a PA for an OFF Band antenna (cf. the detailed description of  FIG. 1 ). In some circumstances the measurement set formed in step  420  may include multiple temperature sensors. Further according to some embodiments, when no IC in the PCB layout is idle (which may be a rare occurrence), step  420  may include adding temperature sensors from the least active dies to the measurement set. Step  430  includes selecting temperature sensors from the measurement set according to the PCB layout. For example, step  420  may include determining which circuits in the measurement set are proximal to a thermal component such as a heat source or a heat sink (e.g., thermal component  220 , cf.  FIG. 2 ). 
       FIG. 5  illustrates a flow chart in a method  500  for thermal control of a portable electronic device, according to some embodiments. A portable electronic device in method  500  may include a PCB layout having dies, each die including a temperature sensor (e.g., PCB  100 , dies  110 , and temperature sensors  101 , cf.  FIG. 1 ). Furthermore, the PCB layout in method  500  may include a processor circuit and a memory circuit (e.g., processor circuit  111  and memory circuit  112 , cf.  FIG. 1 ). Accordingly, steps in method  300  may be partially or completely performed by the processor circuit executing commands, storing data, and using data stored in the memory circuit. In some embodiments, steps in method  400  may be performed in the context of step  330  in method  300 , described in detail above (cf.  FIG. 3 ). 
     Step  510  includes collecting a plurality of temperature readings. Step  510  may include collecting a plurality of temperature readings spread through a period of time. In some embodiments, step  510  may include collecting a plurality of temperature readings from different temperature sensors located in different areas of the PCB layout. Further according to some embodiments, step  510  may include temperature readings from different areas of the PCB layout, and spread through a period of time. In some embodiments, step  510  may include removing certain values from the temperature readings. For example, the maximum temperature reading and the minimum temperature reading in the plurality of temperature readings may be removed. 
     Step  520  includes performing a statistical analysis on the collected temperature readings. Accordingly, step  520  may include forming a histogram of temperature values. Step  520  may further include finding a mean, a median, a maximum, a minimum, and a standard deviation from a distribution of measurement values as collected in step  510 . 
       FIG. 6  illustrates a flow chart in a method  600  for thermal control of a portable electronic device, according to some embodiments. A portable electronic device in method  600  may include a PCB layout having dies, each die including a temperature sensor (e.g., PCB  100 , dies  110 , and temperature sensors  101 , cf.  FIG. 1 ). Furthermore, the PCB layout in method  600  may include a processor circuit and a memory circuit (e.g., processor circuit  111  and memory circuit  112 , cf.  FIG. 1 ). Accordingly, steps in method  300  may be partially or completely performed by the processor circuit executing commands, storing data, and using data stored in the memory circuit. In some embodiments, steps in method  600  may be performed in the context of step  340  in method  300 , described in detail above (cf.  FIG. 3 ). 
     Step  610  includes developing a temperature gradient model. Accordingly, step  610  may include retrieving a temperature gradient model as created in method  300  (cf. step  310 ,  FIG. 3 ). Step  620  includes providing temperature measurement values to the temperature gradient model. Accordingly, step  620  may include determining a temperature gradient measurement. For example, the temperature measurement values may include a plurality of measurement values in a boundary value portion of the PCB layout. The temperature gradient model developed in step  610  may then provide temperature values in a portion of the PCB layout contained by the boundary value portion. 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20130509
Publication Date: 20160315
Grant Date: 20160315
Priority Date: 20130509
Inventors: HERESZTYN AMAURY J.
CHOWDHURY IHTESHAM H.
COX KEITH
Assignee: APPLE INC
CPC Classifications: [{"code": "G01K7/01", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01K7/01", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 51864627