Patent Description:
Integrated circuits (IC), such as analog signal ICs, digital signal ICs, or mixed signal ICs, typically comprise a set of electronic components, such as transistors or other suitable components, inseparably integrated on a relatively small portion of semiconductor material (e.g., silicon or other suitable material). Modern ICs may integrate millions or billions of electronic components and may be used in various applications, such as desktop computers, laptop computers, mobile computing devices, tablet computing devices, home appliances, stereos, medical devices, and a plurality of other electronic devices.

In such applications, an IC is typically connected, using solder or other thermally conductive material, to a printed circuit board (PCB) substrate, which electrically connects other ICs and electronic components on the PCB as described in <CIT>, <CIT>, <CIT> and in <CIT>. Typically, solder and flux (e.g., a paste that promotes solder flow) are applied to the PCB (e.g., using a dipping process or other suitable manufacturing process) to secure and electrically connect the IC, and other electronic components, to the PCB (e.g., typically referred to as a PCB assembly (PCBA) when the ICs and electronic components are secured and electrically connected to the PCB).

During manufacturing of PCBAs, the thermal paths (e.g., solder connections connecting the IC to the substrate of the PCB and/or thermal interface material between the PCB and a pedestal of the PCBA) and/or system level thermal performance of the PCBA may be verified using, for example, X-ray screening processes. However, as power demand in ICs increases, accurate verification of thermal paths and/or the system level thermal performance of the PCBA has become increasingly more difficult.

This disclosure relates generally to integrated circuit thermal path assessment systems and methods.

An aspect of the disclosed embodiments is a method for assessing a thermal path associated with an integrated circuit, according to claim <NUM> of the appended claims.

In the method, the heat application mode may further include at least one of a first test mode and a normal operation mode.

Also in the method, the first test mode may include a low error-heating mode.

In the method, the normal operation mode may correspond to normal operating characteristics of the integrated circuit.

Also in the method, the initial temperature may correspond to a baseline temperature of the design type corresponding to the integrated circuit at a time prior to heat being applied.

The subsequent temperature may corresponds to a temperature of the design type corresponding to the integrated circuit at a time after heat is applied.

Another aspect of the disclosed embodiments is an integrated circuit thermal path assessment system according to claim <NUM> of the appended claims.

The heat application mode may further include a low error-heating mode.

The heat application mode may further include a normal operation mode corresponding to normal operating characteristics of the integrated circuit.

The subsequent temperature may correspond to a temperature of the design type corresponding to the integrated circuit at a time after heat is applied.

These and other aspects of the present disclosure are provided in the following detailed description of the embodiments, the appended claims, and the accompanying figures.

The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.

As described, integrated circuits (IC), such as analog signal ICs, digital signal ICs, or mixed signal ICs, typically comprise a set of electronic components, such as transistors or other suitable components, inseparably integrated on a relatively small portion of semiconductor material (e.g., silicon or other suitable material). ICs may include microprocessors, microcontrollers, memory chips, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), sensors, power management circuits, operation amplifiers, analog-to-digital converters, digital-to-analog converters, and the like. Modern ICs may integrate millions or billions of electronic components and may be used in various applications, such as desktop computers, laptop computers, mobile computing devices, tablet computing devices, home appliances, stereos, medical equipment, and a plurality of other electronic devices.

An IC is typically connected, using solder or other thermally conductive material, to a printed circuit board (PCB) substrate, which electrically connects other ICs and electronic components on the PCB. For example, one or more leads of the IC may be soldered (e.g., thermally attached) to the substrate to electrically connect the IC to the other ICs and electronic components on the PCB and/or to one another. The solder, such as a lead alloy solder or other suitable solder, provides a conductive path for electrons to flow to and from the IC via the substrate. Typically, solder and flux (e.g., a paste that promotes solder flow) are applied to the PCB (e.g., using a dipping process or other suitable manufacturing process) to secure and electrically connect the IC, and other electronic components, to the PCB (e.g., typically referred to as a PCB assembly (PCBA) when the ICs and electronic components are secured and electrically connected to the PCB).

During manufacturing of PCBAs, solder between ICs and/or other electronic components may be insufficiently applied, resulting in faulty solder connections. Faulty solder connections (e.g., solder voids or other faulty solder connection) are relatively common and degrade thermal interfaces (e.g., connections between ICs and/or other electronic components and the substrate). For example, under certain circumstances (e.g., increased thermal conditions resulting from high power being applied to the ICs and/or electronic components) in production (e.g., in a production environment, such as an end user environment, and the like) the solder connection between, for example, the IC and the substrate of the PCB may be inadequate (e.g., due to the insufficiently applied solder). This may cause the IC to overheat or enter thermal shutdown preventing the IC from interacting with other components on the PCB and/or other system components associated therewith. Such faulty solder connections may result from component tolerance issues, leadform stamping tolerances, solder printing tolerances, and the like and are often not detected in the production environment.

Accordingly, during the manufacturing process, the thermal paths (e.g., the solder connections connecting the IC to the substrate of the PCB and/or the thermal interface material between the PCB and a pedestal of the PCBA) and/or system level thermal performance of the PCBA may be inspected and/or verified. For example, X-ray screening processes, visual inspection processors, or other similar processes may be utilized to inspect and/or verify that solder connections of the PCBA are sufficient to allow ICs and/or other electronic components to electrically communicate with one another and to function properly in the production environment under.

However, as power demand in ICs increases, accurate verification of thermal paths and/or the system level thermal performance of the PCBA has become increasingly more difficult. For example, ICs are typically manufactured with a bottom side exposed thermal pad, which is thermally connected with solder or thermally conductive material to the substrate of the PCB. However, such an exposed thermal pad may make solder connection quality and/or thermal structure quality and performance difficult to ensure in a production environment. Additionally, or alternatively, X-ray and/or other screening processes may be subject to variance in user interpretation due to lack of contrast in images of the PCBA captured as part of the X-ray screening processes. Further, such processes are not a quantitative measurement, are subject to visual inspection, and may increase production costs of the ICs and PCBAs. Faulty solder connections and/or other thermal interface faults may not be detected during the manufacturing process, which may increase the likelihood that the PCBAs and/or components associated therewith may fail or have reduced reliability during use in the production environment.

Accordingly, systems and methods, such as those described herein, that verify integrity of system level thermal structure quality during production and that assess thermal characteristics (e.g., solder connections) during engineering development, may be desirable. In some embodiments, the systems and methods described herein may be configured to provide a multi-point thermal path assessment of thermal paths between ICs and substrates of a PCB, a bottom surface of the PCB and a pedestal or case of the PCBA, and the like.

<FIG> generally illustrates a printed circuit board assembly (PCBA) <NUM> according to the principles of the present disclosure. The PCBA <NUM> may be used in any suitable application, such as a desktop computer, a laptop computer, a mobile computing device, a tablet computing device, a home appliance, a stereo, a medical device, or any other suitable electrical device. Additionally, or alternatively, the PCBA <NUM> may interact with a plurality of other PCBAs.

The PCBA <NUM> includes an integrated circuit (IC) <NUM> and a printed circuit board (PCB) <NUM>. The IC <NUM> may include a plurality of electrical components inseparably integrated and/or disposed on a segment of semiconductor material, such as silicon or other suitable semiconductor material. The IC <NUM> may comprise a microprocessor, a microcontroller, a memory chip, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a sensor, a power management circuit, an operation amplifier, an analog-to-digital converter, a digital-to-analog converter, or other suitable IC. Additionally, or alternatively, the IC <NUM> may comprise an analog signal IC, a digital signal IC, or a mixed signal IC. The IC <NUM> may include an exposed pad disposed on a bottom surface of the IC <NUM> (e.g., a surface that faces the PCB <NUM>). The exposed pad may include a plurality of leads adapted to be electrically connected to the PCB <NUM>. For example, as described, thermal conductive material such as solder, may be applied between a respective lead and a portion of a substrate on the PCB <NUM>. It should be understood that while only the IC <NUM> is described herein, the principles of the present disclosure apply to any number of ICs and any suitable electrical components.

The PCB <NUM> may be adapted to mechanically support the IC <NUM> and/or other ICs and electrical components and to electrically connect such components. The PCB <NUM> may include, as described, substrates, pads, and other features that may be etched into one or more layers of conductive material, such as copper or other suitable conductive material. The layers of conductive material of the PCB <NUM> may be laminated onto or sandwiched between layers of non-conductive material.

The PCBA <NUM> may include a pedestal (e.g., a heat sink) <NUM> and a PCBA case or housing <NUM>. In some embodiments, the PCBA housing <NUM> may be configured to house or enclose the IC <NUM>, PCB <NUM>, and/or the pedestal <NUM>. The pedestal <NUM> may be disposed on a side of the PCB <NUM> opposite the IC <NUM>. The PCB <NUM> may be attached to the pedestal <NUM> using a suitable thermal interface material (e.g., thermal glue or other thermally conductive material). The pedestal <NUM> may include a heat sink configured to draw heat generated by the IC <NUM> away from the IC <NUM>.

In some embodiments, the PCBA <NUM> includes one or more temperature sensing devices, such as one or more thermal sensing devices <NUM>. The thermal sensing devices <NUM> may include any temperature-sensing device, such as thermal diodes or other suitable temperature sensing devices. The one or more thermal sensing devices <NUM> may be disposed within the IC <NUM> or external to the IC <NUM>. In some embodiments, a thermal sensing device <NUM> may be disposed proximate to a corresponding heat zone of the IC <NUM>. <FIG> generally illustrates a schematic of the PCBA <NUM> including a plurality of heat zones <NUM>. While the PCBA <NUM> is illustrated with four heat zones <NUM>, it should be understood that the PCBA <NUM> may include any suitable number of heat zones <NUM>.

The PCBA <NUM> may include one or more power sources <NUM>. The power sources <NUM> may include current sources, voltage sources, or other suitable power source. The power sources <NUM> may include a power circuit comprising a voltage source, one or more resistors, one or more capacitors, and/or one or more other suitable electrical components. In some embodiments, the PCBA <NUM> includes a high side power source <NUM> and a low side power source <NUM>, however, the PCBA <NUM> may omit either of the high side power source <NUM> or the low side power source <NUM>. When power (e.g., voltage and/or current) is supplied by one of the power sources <NUM>, the power flows through the components of the IC <NUM> and into the substrate of the PCB <NUM> via the thermal connections between the IC <NUM> and the substrate of the PCB <NUM>, which causes a temperature associated with each respective heat zone <NUM> to increase. The thermal sensing devices <NUM> associated with each respective heat zone <NUM> are adapted to sense and/or measure temperatures associated with the respective heat zones <NUM>.

In some embodiments, the PCBA <NUM> may be in communication with a controller <NUM>. For example, the controller <NUM> may include one or more leads that communicates via an interface, such as a serial peripheral interface, a controlled area network bus, an analog voltage output interface, or other suitable interface, of the PCBA <NUM>. The controller <NUM> may include any suitable controller implemented in hardware, software, or a combination thereof, including, but not limited to, an onboard controller, an application running on a mobile computing device, an application running on a desktop or laptop computer, or other suitable controller. The temperatures measured by thermal sensing devices <NUM> are communicated via the interface to the controller <NUM>. In some embodiments, the controller <NUM> may be housed within the PCBA housing <NUM> and/or disposed external to the PCBA housing <NUM>.

In some embodiments, the controller <NUM> may be configured to characterize the IC <NUM> using the temperatures measured by thermal sensing devices <NUM>. For example, during engineering of the IC <NUM>, the controller <NUM> may monitor temperature increases of the heat zones <NUM> in response to various heat application modes, as will be described. The controller <NUM> determines an initial temperature of the IC <NUM>. For example, the controller <NUM> may receive or measure temperature measurements from one or more of the thermal sensing devices <NUM> prior to one of the power sources <NUM> supplying power to the IC <NUM>. Receiving temperature measurements from the one or more thermal sensing devices <NUM> may include the controller <NUM> measuring temperatures of the one or more thermal sensing devices <NUM>. For example, as will be described, the controller <NUM> may follow a temperature monitoring strategy that includes monitoring one or more than one of the thermal sensing devices <NUM>. The controller <NUM> may determine an average temperature of the temperature measurements received or measured from the one or more thermal sensing devices <NUM>.

The controller <NUM> may then select one of a plurality of heat application modes, as will be described, in order to supply power to the IC <NUM>. The controller <NUM> supplies power to the IC <NUM> according to the selected heat application mode. The controller <NUM> receives or measures temperature measurements, according to the temperature monitoring strategy, from the one or more thermal sensing devices <NUM> after a predetermined period. The predetermined period may be any suitable period, such as <NUM> milliseconds, <NUM> milliseconds, or any suitable period. The controller <NUM> may determine an average temperature of the temperature measurements received or measured from the one or more thermal sensing devices <NUM>. The controller <NUM> stores the average temperature as a subsequent temperature of the IC <NUM>. In some embodiments, the controller <NUM> determines a plurality of subsequent temperatures for a plurality of periods after power is supplied to the IC <NUM>.

The controller <NUM> determines a delta temperature corresponding to a change in temperature between the initial temperature of the IC <NUM> and the subsequent temperature of the IC <NUM> (e.g., after power is supplied to the IC <NUM> for the predetermined period). The delta temperature corresponds to an expected temperature change for the IC <NUM> using the selected heat application mode. The controller <NUM> stores the delta temperature in a register associated with the controller <NUM> and/or the IC <NUM>.

The controller <NUM> may determine a relationship between the delta temperature, the selected heat application mode, an arrangement of the thermal sensing devices <NUM> relative to the heat zones <NUM>, and the temperature monitoring strategy. For example, the controller <NUM> may determine that, for the IC <NUM>, using the selected heat application mode, with the thermal sensing devices <NUM> arranged proximate the heat zones <NUM>, and following the temperature monitoring strategy, the delta temperature is the expected temperature change between an initial temperature and a subsequent temperature measured after a predetermined period following application of power to the IC <NUM>.

As will be described, in some embodiments, during manufacturing of PCBAs having ICs with a similar design to the IC <NUM>, the ICs may be tested to verify sufficiency of thermal paths associated with the ICs. The ICs may be tested at in-circuit test, middle of the line, end of the line, at assembled unit testing, or a combination thereof. A thermal path associated with a respective IC may include solder connections between the IC and an associated PCB, a thermal interface between the PCB and an associated pedestal, a thermal interface between the PCB and the housing, a thermal interface between the IC and the pedestal, a thermal interface between the IC and the housing, and/or other suitable thermal interfaces or connections. For a respective IC, when a measured delta temperature is within a predetermined range (e.g., plus or minus one degree, or other suitable range) of the expected delta temperature, the thermal path associated with the IC (e.g., associated with the heat zones <NUM> that are tested for the IC) are determined to be sufficient. Conversely, for the respective IC, when the measured delta temperature is outside of the predetermined range of the expected delta temperature, the thermal path associated with the IC is determined to be intermediate or insufficient, depending on how far outside the predetermined range the measured delta temperature is. The PCBA may then be repaired in order to correct the insufficient thermal path.

<FIG> generally illustrates a chart <NUM> illustrating delta temperatures between initial temperature measurements <NUM> and subsequent measurements <NUM>. Line <NUM> generally illustrates an expected delta temperature for an IC. Lines <NUM> and <NUM> illustrate measured delta temperatures for an IC having an intermediate thermal path (e.g., line <NUM>) and insufficient thermal path (e.g., line <NUM>).

In some embodiments, the controller <NUM> may select other heat application modes and determine corresponding expected delta temperatures for each respective heat application mode. Additionally, or alternatively, the controller <NUM> may follow other temperature monitoring strategies of a plurality of temperature monitoring strategies. For example, as will be described, a one temperature monitoring strategy may include monitoring one thermal sensing device <NUM> while another temperature monitoring strategy may include determining an average temperature from temperature measurements received or measured from all thermal sensing devices <NUM>. In some embodiments, the controller <NUM> follows each temperature monitoring strategy for each heat application mode and determines relationships, as described, for each combination of temperature monitoring strategy and heat application mode.

The controller <NUM> may determine which combination of temperature monitoring strategy and heat application mode most accurately characterizes the IC <NUM>. For example, the controller <NUM> may communicate with an automatic data processing (ADP) system to determine which combination of temperature monitoring strategy and heat application mode most accurately characterizes the IC <NUM>. The initial temperature, the subsequent temperature, and/or the delta temperature associated with the combination of temperature monitoring strategy and heat application mode most accurately characterizes the IC <NUM> are stored as the expected initial temperature, the expected subsequent temperature, and the expected delta temperature in registers associated with ICs having a similar design type as the IC <NUM>. During manufacturing of the PCBAs, as described, the expected initial temperature, the expected subsequent temperature, and/or the expected delta temperature stored in the registers of the ICs are used to test the ICs, as described.

<FIG> generally illustrates an optional heat application mode, such as a low error-heating mode <NUM> according to the principles of the present disclosure. The mode <NUM> may be referred to as a test mode of an IC <NUM> and may provide: accurate clamp voltage management; accurate current source management; and known power values. The mode <NUM> includes the IC <NUM> (e.g., comprising an ASIC) and a power source <NUM>. The IC <NUM> may include a first circuit design type. The IC <NUM> includes a field-effect transistor (FET) <NUM> and a thermal sensing device <NUM> connected to ground on a low side of the FET <NUM> and the thermal sensing device <NUM> and connected to the power source <NUM> on a high side of the FET <NUM> and the thermal sensing device <NUM>. The thermal sensing device <NUM> may include a thermal diode, as described. Additionally, the IC <NUM> includes a clamp <NUM> connected to the FET <NUM> on a low side of the clamp <NUM> and connected to the power source <NUM> on a high side of the clamp <NUM>.

The mode <NUM> includes supplying power, using the power source <NUM>, to the high side of the IC <NUM>. The power source <NUM> may include a voltage source <NUM> and a current source <NUM>. The voltage source <NUM> may be configured to provide a voltage value. For example, the voltage value may include <NUM> volts or substantially <NUM> volts. The current source <NUM> is configured to provide a current value. For example, the current value may include <NUM> milliamps or substantially <NUM> milliamps. As described, the controller <NUM> is configured to receive or measure, from the thermal sensing device <NUM>, a temperature measurement before power is supplied to the IC <NUM> (e.g., the initial temperature). The controller <NUM> may then supply the power, using the power source <NUM>, to the high side of the IC <NUM> and, after the predetermined period expires and/or in response to the clamp <NUM> opening, the controller <NUM> receives or measures another temperature measurement from the thermal sensing device <NUM> (e.g., the subsequent temperature).

<FIG> generally illustrates an optional alternative heat application mode <NUM>' according to the principles of the present disclosure. The mode <NUM>' may be referred to as a normal operation mode for the IC <NUM>. The mode <NUM>' includes the IC <NUM>, as described, and an alternative power source <NUM>'. The mode <NUM>' includes supplying power, using the power source <NUM>', to the high side of the IC <NUM>. The power source <NUM>' may include an alternative voltage source <NUM>' and a resistor <NUM>. The voltage source <NUM>' may be configured to provide a voltage value. For example, the voltage value may include <NUM> volts or substantially <NUM> volts. The resistor <NUM> is configured to provide a resistance value. For example, the resistance value may include <NUM> ohms or substantially <NUM> ohms. As described, the controller <NUM> is configured to receive or measure, from the thermal sensing device <NUM>, a temperature measurement before power is supplied to the IC <NUM> (e.g., the initial temperature). The controller <NUM> may then supply the power, using the power source <NUM>, to the high side of the IC <NUM> and, after the predetermined period expires and/or in response to the clamp <NUM> opening, the controller <NUM> receives or measures another temperature measurement from the thermal sensing device <NUM> (e.g., the subsequent temperature).

<FIG> generally illustrates an optional alternative heat application mode, an internal timer heat application mode <NUM>" according to the principles of the present disclosure. The mode <NUM>" may be referred to as a test mode of the IC <NUM> and may provide: accurate clamp voltage management; accurate current source management; and known power values. The mode <NUM>" includes the IC <NUM> and the power source <NUM>. The IC <NUM> may include the first circuit design type, as described. For example, the IC <NUM> includes the FET <NUM> and the thermal sensing device <NUM> connected to ground on the low side of the FET <NUM> and the thermal sensing device <NUM> and connected to the power source <NUM> on the high side of the FET <NUM> and the thermal sensing device <NUM>. Additionally, the IC <NUM> includes the clamp <NUM> connected to the FET <NUM> on the low side of the clamp <NUM> and connected to the power source <NUM> on the high side of the clamp <NUM>. The IC <NUM> may further include a timer <NUM>. The timer <NUM> may be connected to a voltage drain on one side of the timer <NUM> and a voltage output on another side of the timer <NUM>. The timer <NUM> is configured to time a period corresponding to the predetermined period, as described, for measuring subsequent temperatures of the thermal sensing device <NUM>. The timer <NUM> may begin timing the period in response to power being supplied, by the power source <NUM>, to the IC <NUM>. The timer <NUM> may stop timing when the timer <NUM> reaches an end of the period (e.g., <NUM> milliseconds, <NUM> milliseconds, or any suitable period). The controller <NUM>, as described, may receive or measure a temperature measurement from one or more of the thermal sensing devices <NUM> in response to the timer <NUM> reaching the end of the period.

The mode <NUM>" includes supplying power, using the power source <NUM>, to the high side of the IC <NUM>. The power source <NUM> may include the voltage source <NUM> and the current source <NUM>. The voltage source <NUM> may be configured to provide a voltage value. For example, the voltage value may include <NUM> volts or substantially <NUM> volts. The current source <NUM> is configured to provide a current value. For example, the current value may include <NUM> milliamps or substantially <NUM> milliamps. As described, the controller <NUM> is configured to receive or measure, from the thermal sensing device <NUM>, a temperature measurement before power is supplied to the IC <NUM> (e.g., the initial temperature). The controller <NUM> may then supply the power, using the power source <NUM>, to the high side of the IC <NUM> and, after the predetermined period expires (e.g., in response to the timer <NUM> reaching the end of the period) and/or in response to the clamp <NUM> opening, the controller <NUM> receives or measures another temperature measurement from the thermal sensing device <NUM> (e.g., the subsequent temperature).

<FIG> generally illustrates a heat application mode, that is a current limit mode <NUM>, according to the principles of the present disclosure. The mode <NUM> includes an IC <NUM> (e.g., comprising an ASIC) and a power source <NUM>. The IC <NUM> may include a second circuit design type. The IC <NUM> includes a FET <NUM> and a thermal sensing device <NUM> connected to a resistor <NUM> on a low side of the FET <NUM> and the thermal sensing device <NUM> and connected to the power source <NUM> on a high side of the FET <NUM> and the thermal sensing device <NUM>. The thermal sensing device <NUM> may include a thermal diode, as described. The resistor <NUM> is disposed on a PCB external from the IC <NUM> and is connected to ground on a side of the resistor <NUM> opposite the FET <NUM> and the thermal sensing device <NUM>. The resistor <NUM> is configured to provide a resistance value. The resistance value may be relatively low (e.g., <NUM> ohms or substantially <NUM> ohms) in order to force a current limit of the IC <NUM> to activate, which may result in a relatively large amount of power. The mode <NUM> may be referred to as a test mode of an IC <NUM> and may provide: accurate voltage measurement; and known power values using measurements of current through the resistor <NUM>.

The mode <NUM> includes supplying power, using the power source <NUM>, to the high side of the IC <NUM>. The power source <NUM> may include a voltage source. The voltage source may be configured to provide a voltage value. For example, the voltage value may include <NUM> volts or substantially <NUM> volts. As described, the controller <NUM> is configured to receive or measure, from the thermal sensing device <NUM>, a temperature measurement before power is supplied to the IC <NUM> (e.g., the initial temperature). The controller <NUM> may then supply the power, using the power source <NUM>, to the high side of the IC <NUM> and, after the predetermined period, the controller <NUM> receives or measures another temperature measurement from the thermal sensing device <NUM> (e.g., the subsequent temperature).

<FIG> generally illustrates an alternative heat application mode <NUM>' according to the principles of the present disclosure. The mode <NUM>' includes the IC <NUM> and the power source <NUM>. The IC <NUM> includes the FET <NUM> and the thermal sensing device <NUM> connected to an alternative resistor <NUM>' on the low side of the FET <NUM> and the thermal sensing device <NUM> and connected to the power source <NUM> on the high side of the FET <NUM> and the thermal sensing device <NUM>. The thermal sensing device <NUM> may include a thermal diode, as described. The resistor <NUM>' is disposed on a PCB external from the IC <NUM> and is connected to ground on the side of the resistor <NUM>' opposite the FET <NUM> and the thermal sensing device <NUM>. The resistor <NUM>' is configured to provide a resistance value. The resistance value may be relatively higher than the resistor <NUM> of <FIG>(e.g., <NUM> ohms or substantially <NUM> ohms). The resistance value of the resistor <NUM>' may be set for a rated current, which may result in a relatively small amount of power. The mode <NUM>' may be referred to as a test mode of an IC <NUM>.

The mode <NUM>' includes supplying power, using the power source <NUM>, to the high side of the IC <NUM>. The power source <NUM> may include a voltage source. The voltage source may be configured to provide a voltage value. For example, the voltage value may include <NUM> volts or substantially <NUM> volts. As described, the controller <NUM> is configured to receive or measure, from the thermal sensing device <NUM>, a temperature measurement before power is supplied to the IC <NUM> (e.g., the initial temperature). The controller <NUM> may then supply the power, using the power source <NUM>, to the high side of the IC <NUM> and, after the predetermined period, the controller <NUM> receives or measures another temperature measurement from the thermal sensing device <NUM> (e.g., the subsequent temperature).

<FIG> generally illustrates a schematic of a printed circuit board assembly (PCBA) <NUM> according to the principles of the present disclosure. The PCBA <NUM> may include features similar to those of the PCBA <NUM>, as described. For example, the PCBA <NUM> includes an IC <NUM> and a PCB <NUM>. The IC <NUM> may include features similar to those described with respect to any of the ICs described herein. For example, the IC <NUM> includes a plurality of thermal sensing devices <NUM> disposed proximate respective heat zones 408A-408C. While the IC <NUM> is illustrated having heat zones 408A-408C, it should be understood that the IC <NUM> may include any suitable number of heat zones and any suitable number of corresponding thermal sensing devices. The IC <NUM> may be configured according to the first circuit design type, the second circuit design type, or any suitable circuit design type. Accordingly, any of the heat application modes described herein may be used to apply heat to the IC <NUM>.

The PCB <NUM> may include features similar to those described with respect to any of the PCBs described herein. The PCBA400 includes a plurality of power sources <NUM>. The power sources <NUM> may include features similar to those described with respect to any of the power sources described herein. In some embodiments, the PCBA <NUM> includes a PCBA housing <NUM> configured to house or enclose the IC <NUM> and/or the PCB <NUM>. In some embodiments, a controller, such as the controller <NUM> may be housed within the PCBA housing <NUM> and/or disposed external to the PCBA housing <NUM>.

As described, the controller <NUM> may follow one of a plurality of temperature monitoring strategies when characterizing the IC <NUM> and/or during manufacturing of PCBAs having ICs with a similar circuit design type as the IC <NUM> to determine whether thermal paths associated with the IC <NUM> are sufficient. In some embodiments, a first temperature monitoring strategy includes applying heat, according to a selected heat application mode, to each of the thermal sensing devices <NUM> simultaneously or substantially simultaneously. For example, the controller <NUM> may receive or measure an initial temperature measurement from each of the thermal sensing devices <NUM>. The controller <NUM> supplies power, using each of the power sources <NUM>, to each of the thermal sensing devices <NUM>, according to the selected heat application mode, at the same time. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from one of the thermal sensing devices <NUM>. The controller <NUM> may determine a delta temperature for the thermal sensing device <NUM>. The controller <NUM> may then store the initial temperatures, the subsequent temperature, and the delta temperature in a register associated with the IC <NUM> and/or ICs having a similar circuit design as the IC <NUM>. Additionally, or alternatively, the controller <NUM> may define and store thermal relationships of the IC <NUM>, as described.

During manufacturing of the PCBAs having ICs with a similar circuit design as the IC <NUM>, the controller <NUM> may receive or measure an initial temperature measurement from each of the thermal sensing devices associated with an IC. The controller <NUM> supplies power, using each of the power sources associated with the IC, to each of the thermal sensing devices associated with the IC, according to the selected heat application mode, at the same time. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from one of the thermal sensing devices associated with the IC. The controller <NUM> may determine a delta temperature for the thermal sensing device. The controller <NUM> may retrieve, from a register associated with the IC, the expected delta temperature. The controller <NUM> may then compare the delta temperature for the thermal sensing device to the expected temperature and determine whether thermal paths proximate to the heat zone associated with the thermal sensing device are sufficient based on the comparison, as described.

In some embodiments, a second temperature monitoring strategy includes applying heat, according to a selected heat application mode, to each of the thermal sensing devices <NUM> simultaneously or substantially simultaneously, as described. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from each of the thermal sensing devices <NUM>. The controller <NUM> may determine a delta temperature for each of the thermal sensing devices <NUM>. The controller <NUM> may then store the initial temperatures, the subsequent temperatures, and the delta temperatures in a register associated with the IC <NUM> and/or ICs having a similar circuit design as the IC <NUM>. Additionally, or alternatively, the controller <NUM> may define and store thermal relationships of the IC <NUM>, as described.

During manufacturing of the PCBAs having ICs with a similar circuit design as the IC <NUM>, the controller <NUM> may receive or measure an initial temperature measurement from each of the thermal sensing devices associated with an IC. The controller <NUM> supplies power, using each of the power sources associated with the IC, to each of the thermal sensing devices associated with the IC, according to the selected heat application mode, at the same time. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from each of the thermal sensing devices associated with the IC. The controller <NUM> may determine delta temperatures for each of the thermal sensing devices. The controller <NUM> may retrieve, from a register associated with the IC, the expected delta temperatures corresponding to each of the thermal sensing devices and compare the delta temperatures for each respective thermal sensing device to the expected temperature corresponding to the respective thermal sensing device. The controller <NUM> may determine whether thermal paths proximate to the heat zone associated with the thermal sensing device are sufficient based on the comparison, as described.

In some embodiments, a third temperature monitoring strategy includes applying heat, according to a selected heat application mode, to one of the thermal sensing devices <NUM>. For example, the controller <NUM> may receive or measure an initial temperature measurement from one or all of the thermal sensing devices <NUM>. The controller <NUM> supplies power, using one of the power sources <NUM>, to one of the thermal sensing devices <NUM>, according to the selected heat application mode. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from the thermal sensing device <NUM>. The controller <NUM> may determine a delta temperature for the thermal sensing device <NUM>. The controller <NUM> may then store the initial temperatures, the subsequent temperature, and the delta temperature in a register associated with the IC <NUM> and/or ICs having a similar circuit design as the IC <NUM>. Additionally, or alternatively, the controller <NUM> may define and store thermal relationships of the IC <NUM>, as described.

During manufacturing of the PCBAs having ICs with a similar circuit design as the IC <NUM>, the controller <NUM> may receive or measure an initial temperature measurement from one or all of the thermal sensing devices associated with an IC. The controller <NUM> supplies power, using one of the power sources associated with the IC, to one of the thermal sensing devices associated with the IC, according to the selected heat application mode. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from the thermal sensing device associated with the IC. The controller <NUM> may determine a delta temperature for the thermal sensing device. The controller <NUM> may retrieve, from a register associated with the IC, the expected delta temperature. The controller <NUM> may then compare the delta temperature for the thermal sensing device to the expected temperature and determine whether thermal paths proximate to the heat zone associated with the thermal sensing device are sufficient based on the comparison, as described.

In some embodiments, a fourth temperature monitoring strategy includes applying heat, according to a selected heat application mode, to each of the thermal sensing devices <NUM>, individually. For example, the controller <NUM> may receive or measure an initial temperature measurement from each of the thermal sensing devices <NUM>. The controller <NUM> supplies power, using one of the power sources <NUM>, to a first thermal sensing device <NUM>, according to the selected heat application mode. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from the first thermal sensing device <NUM>. The controller <NUM> may determine a first delta temperature for the first thermal sensing device <NUM>. The controller <NUM> may then store the initial temperatures, the subsequent temperature, and the first delta temperature in a register associated with the IC <NUM> and/or ICs having a similar circuit design as the IC <NUM>.

The controller <NUM> supplies power, using another of the power sources <NUM>, to a second thermal sensing device <NUM>, according to the selected heat application mode. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from the second thermal sensing device <NUM>. The controller <NUM> may determine a second delta temperature for the second thermal sensing device <NUM>. The controller <NUM> may then store the initial temperatures, the subsequent temperature, and the second delta temperature in a register associated with the IC <NUM> and/or ICs having a similar circuit design as the IC <NUM>. The controller <NUM> may continue for each of the thermal sensing devices <NUM> of the IC <NUM>. Additionally, or alternatively, the controller <NUM> may define and store thermal relationships of the IC <NUM>, as described.

During manufacturing of the PCBAs having ICs with a similar circuit design as the IC <NUM>, the controller <NUM> may receive or measure an initial temperature measurement from each of the thermal sensing devices associated with an IC. The controller <NUM> supplies power, using one of the power sources associated with the IC, to a first thermal sensing device associated with the IC, according to the selected heat application mode. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from the first thermal sensing device associated with the IC. The controller <NUM> may determine a first delta temperature for the thermal sensing device. The controller <NUM> may retrieve, from a register associated with the IC, the first expected delta temperature. The controller <NUM> may then compare the first delta temperature for the first thermal sensing device to the first expected temperature and determine whether thermal paths proximate to the heat zone associated with the first thermal sensing device are sufficient based on the comparison, as described. The controller <NUM> may continue for each of the thermal sensing devices associated with the ICs having a circuit design type similar to the IC <NUM>.

In some embodiments, during manufacturing of the PCBAs having ICs with a similar circuit design as the IC <NUM>, the controller <NUM> may receive or measure an initial temperature measurement from each of the thermal sensing devices associated with an IC. The controller <NUM> supplies power, using one of the power sources associated with the IC, to a first thermal sensing device associated with the IC, according to the selected heat application mode. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from the first thermal sensing device associated with the IC. The controller <NUM> may determine a first delta temperature for the thermal sensing device.

The controller <NUM> may then supply power, using another of the power sources associated with the IC, to a second thermal sensing device associated with the IC, according to the selected heat application mode. The controller <NUM> may then receive or measure temperature measurements (e.g., subsequent temperature measurements) from the second thermal sensing device associated with the IC. The controller <NUM> may determine a second delta temperature for the thermal sensing device. The controller <NUM> may continue for each of the thermal sensing devices associated with the IC. The controller <NUM> may compare each of the first delta temperature, the second delta temperature, and other delta temperatures of the IC. The controller <NUM> may determine thermal paths proximate to one or more heat zones of the IC are insufficient, based on the comparison. For example, the controller <NUM> may determine that one of the delta temperatures associated with one of the thermal sensing devices is outside of a range of the other delta temperatures. The controller <NUM> may determine that the delta temperature outside of the range of the other delta temperatures indicates insufficient thermal paths proximate to the heat zone associated with the thermal sensing device having the delta temperature outside the range of the other delta temperatures. It should be understood that while only limited examples are described herein, the principles of the present disclose apply to any suitable temperature monitoring strategy other than those described herein. Additionally, or alternatively, the controller <NUM> may apply heat, according to a heat application mode, to one, some, or all of the thermal sensing devices in any suitable order. The controller <NUM> may use the same power source to supply power, according to the heat application mode to one, some, or all of the thermal sensing devices and/or the controller <NUM> may use different power sources.

In some embodiments, the controller <NUM> may perform the methods described herein. However, the methods described herein as performed by the controller <NUM> are not meant to be limiting, and any type of software executed on a controller can perform the methods described herein without departing from the scope of this disclosure. For example, a controller, such as a processor executing software within a computing device onboard the PCBAs <NUM>,<NUM> or external to the PCBAs <NUM>,<NUM>, can perform the methods described herein.

<FIG> is a flow diagram generally illustrating an integrated circuit characterization method <NUM> according to the principles of the present disclosure. At <NUM>, the method <NUM> measures an initial temperature of an integrated circuit. As described, the controller <NUM> may receive or measure initial temperatures for one or all of the thermal sensing devices <NUM> of the IC <NUM>. At <NUM>, the method <NUM> applies heat according to a heat application mode. As described, the controller <NUM> may apply heat to one or more of the thermal sensing devices <NUM> according to a selected heat application mode using one or more of the power sources <NUM>. At <NUM>, the method <NUM> measures subsequent temperatures of the integrated circuit. As described, the controller <NUM> may receive or measure subsequent temperatures of the one or more thermal sensing devices <NUM> after a predetermined period. The controller <NUM> determines one or more expected delta temperatures, according to the temperature monitoring strategy, as described.

At <NUM>, the method <NUM> determines thermal relationships for the integrated circuit. As described, the controller <NUM> may define a relationship between the expected delta temperature(s), the selected heat application mode, an arrangement of the thermal sensing devices <NUM> relative to the heat zones <NUM>, and the temperature monitoring strategy. At <NUM>, the method <NUM> generates temperature metrics for the integrated circuit. As described, the controller <NUM> may store the initial temperatures, the subsequent temperatures, the delta temperatures, and the relationship definition in registers associated with the IC <NUM> and/or ICs having a similar circuit design type as the IC <NUM>.

<FIG> is a flow diagram generally illustrating a multi-point assessment method <NUM> according to the principles of the present disclosure. At <NUM>, the method <NUM> determines a design type for an integrated circuit. For example, during manufacturing of PCBAs, the controller <NUM> may determine a circuit design type for the ICs. The controller <NUM> may identify, or retrieve from a register, temperature metrics associated with the circuit design type. In some embodiments, the temperature metrics associated with the circuit design type may be stored in registers associated with the ICs. Accordingly, the controller <NUM> may omit determining the circuit design type and may instead retrieve the temperature metrics from the registers. At <NUM>, the method <NUM> identifies a heat application mode based on the design type. The controller <NUM> may determine the heat application mode based on the thermal relationship information stored in the registers (e.g., with the temperature metrics). At <NUM>, the method <NUM> measures a first temperature of the integrated circuit. As described, the controller <NUM> may measure an initial temperature for one or all of the thermal sensing devices associated with an IC being manufactured according to the temperature monitoring strategy.

At <NUM>, the method <NUM> applies heat to the integrated circuit according to a heat application mode. As described, the controller <NUM> applies heat, using one or more power sources associated with the IC, to one or more thermal sensing devices of the IC, according to a heat application mode identified based on the circuit design type and/or stored in the register associated with the IC. At <NUM>, the method <NUM> measures second temperatures of the integrated circuit. As described, the controller <NUM> receives or measures a subsequent temperature for the one or more thermal sensing devices, according to the temperature monitoring strategy. At <NUM>, the method <NUM> determines a difference between the first temperature the second temperature. As described, the controller <NUM> determines a delta temperature for the one or more thermal sensing devices by determining a difference between the initial temperature of the one or more thermal sensing devices and the subsequent temperature of the one or more thermal sensing devices. At <NUM>, the method <NUM> compares the difference to predetermined temperature metrics for the integrated circuit. As described, the controller <NUM> compares the delta temperature for the one or more thermal sensing devices to a corresponding expected delta temperature stored in the register associated with the IC. At <NUM>, the method <NUM> determines whether thermal path is sufficient based on the comparison. As described, the controller <NUM> may determine whether thermal path associated with a heat zone corresponding to the one or more thermal sensing devices is sufficient based on the comparison between the delta temperature and the expected delta temperature.

In some embodiments, the method <NUM>, as described, may be performed, using the controller <NUM>, at in-circuit testing or middle of the line testing (e.g., on the IC and PCB prior to a pedestal and/or housing being assembled within the associated PCBA) and then again at end of the line testing. For example, the controller <NUM> may determine, by performing the method <NUM>, whether solder connections (e.g., of the thermal path) between the IC and the PCB are sufficient. For example, if the controller <NUM> determines delta temperature is within the predetermined range of the expected delta temperature, the controller <NUM> determines that the solder connections between the IC and the PCB are sufficient. The associated PCBA may then continue through the manufacturing process. Conversely, if the controller <NUM> determines the delta temperature is outside of the predetermined range of the expected temperature, the controller <NUM> determines that solder connections between the IC and the PCB are intermediate or insufficient. The solder connections between the IC and the PCB may be repaired before the PCBA continues through the manufacturing process.

During end of line testing, the controller <NUM> may determine, by performing the method <NUM>, whether the thermal interface (e.g., of the thermal path) between the PCB and the pedestal or the housing is sufficient. For example, if the controller <NUM> determines that the delta temperature is within the predetermined range of the expected delta temperature, the controller <NUM> determines that the thermal interface between the PCB and the pedestal or the housing is sufficient. Additionally, or alternatively, the controller <NUM> determines, based on the determination that the delta temperature is within the predetermined range of the expected delta temperature, that the thermal path of the PCBA is sufficient (e.g., because the solder connections between the IC and the PCB were previously determined to be sufficient).

Conversely, during end of line testing, if the controller <NUM> determines that the delta temperature is outside of the predetermined range of the expected delta temperature, the controller <NUM> determines that the thermal interface between the PCB and the pedestal or the housing is intermediate or insufficient. The PCBA may be scrapped or the thermal interface may be repaired based on the determination that the thermal interface between the PCB and the pedestal is intermediate or insufficient.

In some embodiments, the method <NUM>, as described, may be performed, using the controller <NUM>, at in-circuit testing or middle of the line testing (e.g., on the IC and PCB prior to a pedestal and/or housing being assembled within the associated PCBA). For example, the controller <NUM> may determine, by performing the method <NUM>, whether solder connections (e.g., of the thermal path) between the IC and the PCB are sufficient. For example, if the controller <NUM> determines delta temperature is within the predetermined range of the expected delta temperature, the controller <NUM> determines that the solder connections between the IC and the PCB are sufficient. The associated PCBA may then continue through the manufacturing process. Conversely, if the controller <NUM> determines the delta temperature is outside of the predetermined range of the expected temperature, the controller <NUM> determines that solder connections between the IC and the PCB are intermediate or insufficient. The solder connections between the IC and the PCB may be repaired before the PCBA continues through the manufacturing process. Thermal paths of the PCBA during finally assembly of the PCBA (e.g., including the pedestal and housing) may be assumed to be sufficient based on a determination that the solder connections between the IC and the PCB are sufficient.

In some embodiments, the method <NUM>, as described, may be performed, using the controller <NUM>, at end of the line testing. For example, the controller <NUM> may determine, by performing the method <NUM>, whether the any portion of the thermal path (e.g., solder connections between the IC and the PCB, the thermal interface between the PCB and the pedestal, and/or other thermal interfaces or connections of the PCBA) is sufficient. For example, if the controller <NUM> determines that the delta temperature is within the predetermined range of the expected delta temperature, the controller <NUM> determines that the thermal path is sufficient. Conversely, if the controller <NUM> determines that the delta temperature is outside of the predetermined range of the expected delta temperature, the controller <NUM> determines that at least one portion of the thermal path is intermediate or insufficient. The PCBA may be scrapped, as repair may be difficult or impossible without knowing which portion of the thermal path is intermediate or insufficient.

In some embodiments, the method <NUM>, as described, may be performed, using the controller <NUM>, during assembled unit testing. For example, the controller <NUM> may determine, by performing the method <NUM>, whether the any portion of the thermal path (e.g., solder connections between the IC and the PCB, the thermal interface between the PCB and the pedestal or the housing, and/or other thermal interfaces or connections of the PCBA) is sufficient. For example, if the controller <NUM> determines that the delta temperature is within the predetermined range of the expected delta temperature, the controller <NUM> determines that the thermal path is sufficient. Conversely, if the controller <NUM> determines that the delta temperature is outside of the predetermined range of the expected delta temperature, the controller <NUM> determines that at least one portion of the thermal path is intermediate or insufficient. The PCBA may be scrapped, as repair may be difficult or impossible without knowing which portion of the thermal path is intermediate or insufficient. Assembled unit testing results may be used during engineering debugging of initial PCBAs (e.g., during characterization, as described) to verify good components.

The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.

The word "example" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "example" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word "example" is intended to present concepts in a concrete fashion. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless specified otherwise, or clear from context, "X includes A or B" is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then "X includes A or B" is satisfied under any of the foregoing instances. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form. Moreover, use of the term "an implementation" or "one implementation" throughout is not intended to mean the same embodiment or implementation unless described as such.

Implementations of the systems, algorithms, methods, instructions, etc., described herein can be realized in hardware, software, or any combination thereof. The hardware can include, for example, computers, intellectual property (IP) cores, application-specific integrated circuits (ASICs), programmable logic arrays, optical processors, programmable logic controllers, microcode, microcontrollers, servers, microprocessors, digital signal processors, or any other suitable circuit. In the claims, the term "processor" should be understood as encompassing any of the foregoing hardware, either singly or in combination. The terms "signal" and "data" are used interchangeably.

As used herein, the term module can include a packaged functional hardware unit designed for use with other components, a set of instructions executable by a controller (e.g., a processor executing software or firmware), processing circuitry configured to perform a particular function, and a self-contained hardware or software component that interfaces with a larger system. For example, a module can include an application specific integrated circuit (ASIC), a Field Programmable Gate Array (FPGA), a circuit, digital logic circuit, an analog circuit, a combination of discrete circuits, gates, and other types of hardware or combination thereof In other embodiments, a module can include memory that stores instructions executable by a controller to implement a feature of the module.

Further, in one aspect, for example, systems described herein can be implemented using a general-purpose computer or general-purpose processor with a computer program that, when executed, carries out any of the respective methods, algorithms, and/or instructions described herein. In addition, or alternatively, for example, a special purpose computer/processor can be utilized which can contain other hardware for carrying out any of the methods, algorithms, or instructions described herein.

Claim 1:
A method (<NUM>) for assessing a thermal path associated with an integrated circuit (<NUM>, <NUM>, <NUM>, <NUM>) configured to be connected to a power source (<NUM>), the method (<NUM>) comprising:
in response to identifying (<NUM>) that a heat application mode based on a design type of the integrated circuit (<NUM>, <NUM>, <NUM>, <NUM>) is that of a current limit mode (<NUM>):
measuring (<NUM>) a first temperature of at least one thermal sensing device (<NUM>, <NUM>, <NUM>, <NUM>) associated with the integrated circuit (<NUM>, <NUM>, <NUM>, <NUM>);
applying heat (<NUM>) to at least a portion of the integrated circuit (<NUM>, <NUM>, <NUM>, <NUM>) according to the heat application mode;
measuring a second temperature (<NUM>) of the at least one thermal sensing device (<NUM>, <NUM>, <NUM>, <NUM>) associated with the integrated circuit (<NUM>, <NUM>, <NUM>, <NUM>);
determining (<NUM>) a difference between the first temperature and the second temperature; and
determining (<NUM>) whether a thermal path between the integrated circuit and an associated substrate is sufficient based on a comparison (<NUM>) of the difference between the first temperature and the second temperature with a predetermined difference between an initial temperature and a subsequent temperature of the at least one thermal sensing device (<NUM>, <NUM>, <NUM>, <NUM>) and,
wherein the integrated circuit (<NUM>) includes a FET (<NUM>) and the thermal sensing device (<NUM>) connected to a resistor (<NUM>) on a low side of the FET (<NUM>) and the thermal sensing device (<NUM>) and connected to the power source (<NUM>) on a high side of the FET (<NUM>) and the thermal sensing device (<NUM>), the resistor (<NUM>) being disposed on a PCB external from the integrated circuit (<NUM>) and connected to ground on a side of the resistor (<NUM>) opposite the FET (<NUM>) and the thermal sensing device (<NUM>).