Patent Publication Number: US-2023152826-A1

Title: On chip programmable temperature regulation circuit

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to temperature regulation of semiconductor components within on chip systems, and more particularly to programmable temperature control circuits provided on chip and methods of operating such programmable temperature regulation circuits. 
     BACKGROUND OF THE DISCLOSURE 
     Within the field of semiconductor circuits, certain categories of circuitry require a reliable operation over a range of temperatures. For battery management system (BMS) products, for example, accuracy may have to be achievable over a wide temperature range, such as from about −40° C. to about 125° C. In order to guarantee such accuracy, each part is calibrated at multiple different temperatures, for example 90° C., −40° C. and 27° C. in the case of BMS chips. Such temperature insertions are usually performed at Final Test on the packaged parts. Such testing significantly contributes to the cost of manufacturing and is a real concern in terms of competitivity of products. 
     For at least one or more of these reasons, or one or more other reasons, it would be advantageous if new or improved systems could be developed, and/or improved methods of operation or implementation could be developed, so as to address any one or more of the concerns discussed above or to address one or more other concerns or provide one or more benefits. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Specific examples have been chosen for purposes of illustration and description, and are shown in the accompanying drawings, forming a part of the specification. 
         FIG.  1    is a schematic circuit diagram of one embodiment of a programmable temperature regulation circuit of the present technology, at a first point in time. 
         FIG.  2    is a schematic circuit diagram of the programmable temperature regulation circuit of  FIG.  1   , at a subsequent point in time. 
         FIG.  3    is a top plan layout view of a heating element of the programmable temperature regulation circuit of  FIG.  1   . 
         FIG.  4    is a top plan layout view of one example of the programmable temperature regulation circuit of  FIG.  1   , having the reference voltage on chip. 
         FIG.  5    is a top plan layout view of another example of programmable temperature regulation circuit of  FIG.  1   , having the reference voltage external to the chip. 
         FIG.  6    is a flow chart illustrating one method of operating a programmable temperature regulation circuit of  FIG.  1   . 
         FIG.  7    is a schematic circuit diagram of a second embodiment of a programmable temperature regulation circuit of the present technology. 
     
    
    
     While various embodiments discussed herein are amenable to modifications and alternative forms, aspects thereof have been shown by way of example in the drawings and are described in detail herein. It should be understood, however, that the disclosure is not limited to the particular embodiments described, and instead is meant to include all modifications, equivalents, and alternatives falling within the scope of the disclosure. In addition, the terms “example” and “embodiment” as used throughout this application is only by way of illustration, and not limitation, the Figures are not necessarily drawn to scale, and the use of the same reference symbols in different drawings indicates similar or identical items unless otherwise noted. 
     DETAILED DESCRIPTION 
     Programmable temperature regulation circuits, and methods of operating programmable temperature regulation circuits, are described herein for providing heat to an area on a chip. Programmable temperature regulation circuits may be used with a variety of on chip systems, such as any precision measurement circuits where wide operating temperature range, trim and/or calibration are required, including but not limited to battery management system (BMS) products. Programmable temperature regulation circuits of the present technology can be used for several purposes. For example, they can be used for calibration at test. Additionally, since all components of programmable temperature regulation circuits of the present technology may be included on chip, in circumstances where power consumption profiles allow, heating can be provided during normal operation of the on chip system, which may allow regulation of the operating temperature of temperature sensitive components on the chip. Such heating during normal operation may allow improved accuracy performance over the whole operating temperature range. 
     Generally, programmable temperature regulation circuits of the present technology include a heating element that provides heat to a target area on a chip in a controlled manner. The target area may be at least a portion of the area of a chip. The heat provided by the heating element can raise the temperature of the target area to a desired temperature. Components of the on chip system that are particularly temperature sensitive and/or critical to accuracy, like a reference voltage for example, may be placed within the target area, so that the effect of temperature on accuracy can be measured and mathematically compensated. 
       FIGS.  1 - 5    show examples of one embodiment of a programmable temperature regulation circuit  100  of the present technology. The programmable temperature regulation circuit  100  includes a first heating element  102 , a first regulation loop  104  operatively connected to the heating element, and a reference voltage  106 . 
     Referring to  FIGS.  1 - 3   , the first heating element  102  converts electrical power to heat. The first heating element  102  can be a transistor, and in at least some examples, can be an n-channel metal-oxide semiconductor (NMOS) transistor. In other examples, the first heating element  102  can be a different type of transistor, such as a P-channel metal-oxide semiconductor (PMOS) transistor, or a bipolar transistor. 
     The first heating element  102  as shown in the illustrated example defines a closed boundary  108 . The target area  118  to be heated by the first heating element  102  in the illustrated example is the area within the closed boundary  108 . The closed boundary  108  is shown as being in a rectangular shape, but can be in any suitable shape, including having any number of sides, having rounded or straight edges, and being regular or irregular. However, the heating gradient within closed boundary  108  may be more evenly distributed, and may be more accurately controlled, when the closed boundary  108  is symmetrical in shape. 
     Additionally, the first heating element  102  is not limited to being a shape that defines a closed boundary. The first heating element  102  may be in any suitable shape, including without limitation, a line segment, a curve, a zig zag, or a partially closed boundary having an opening. 
     As best shown in  FIG.  1   , the first regulation loop  104  is operatively connected to the first heating element  102 . The first regulation loop  104  provides a first amount of electrical power to the first heating element  102 . The first regulation loop  104  includes at least a first operational transconductance amplifier  110 , and at least a first diode  112 . The first operational transconductance amplifier  110  can be an amplifier configured such that its differential input voltage produces an output current. Thus, it can be a voltage controlled current source (VCCS). The first operational transconductance amplifier  110  is configured to receive a reference temperature voltage  114  and a first temperature feedback voltage  116 . The first diode  112  provides the first temperature feedback voltage  116  to the first operational transconductance amplifier  110 . The reference voltage  106  provides the reference temperature voltage  114  to the first operational transconductance amplifier  110 . 
     Accordingly, at a first point in time during operation, the first operational transconductance amplifier  110  receives the first temperature feedback voltage  116  from the first diode  112  and the reference temperature voltage  114  from the reference voltage  106 , and generates a first output voltage  120  based at least in part on the first temperature feedback voltage  116  and the reference temperature voltage  114 . The first output voltage  120  generated by the first operational transconductance amplifier  110  controls the provision of the first amount of electrical power provided to the first heating element  102 . The first heating element  102  converts the first amount of electrical power to heat, and provides heat to the target area, such as the area  118  within the closed boundary  108  defined by the first heating element  102 . 
     Referring to  FIG.  2   , as time passes during operation of the programmable temperature regulation circuit  100 , the temperature within the target area is expected to change over time, in response to receiving heat generated by the first heating element  102 , and potentially other factors. Additionally, the reference temperature may change, such as if an operator of the system alters the reference temperature. For example, at least one temperature sensor, or a plurality of temperature sensors, can be placed within the target area  118 , such as temperature sensor  138  and temperature sensor  140  shown in  FIGS.  1  and  2   . The temperature sensors  138  and  140  can provide temperature measurements to the operator of the system, and thus allow the operator to monitor the temperature within the target area  118 . Particularly in examples where the target area  118  is relatively large, it may be desirable to place a plurality of temperature sensing elements in different locations inside the heater ring, so that the temperature gradient can be monitored across the whole target area. Depending upon the results of the temperature measurements, the operator may adjust the reference temperature, and thus the reference temperature voltage  114 . 
     Thus, the first operational transconductance amplifier  110  can generate at least one subsequent output voltage to adjust, maintain, or otherwise control the amount of heat being generated by the first heating element  102 . Preferably, the first operational transconductance amplifier  110  can periodically generate subsequent output voltages to adjust, maintain, or otherwise control the amount of heat being generated by the first heating element  102 . Accordingly, at a second point in time, after the first operational transconductance amplifier  110  generates a first output voltage  120 , the first diode can generate at least one subsequent temperature feedback voltage  132 , and the reference voltage  106  can generate a subsequent reference temperature voltage  134 . The first operational transconductance amplifier  110  can receive a subsequent temperature feedback voltage  132  from the first diode  112  and a subsequent reference temperature voltage  134  from the reference voltage  106 , and can generate a subsequent output voltage  136  based at least in part on the subsequent temperature feedback voltage  132  and the subsequent reference temperature voltage  134 . The subsequent output voltage  136  generated by the first operational transconductance amplifier  110  controls a subsequent amount of electrical power provided to the first heating element  102 . The first heating element  102  converts the subsequent amount of electrical power to heat, and provides heat to the target area, such as the area  118  within the closed boundary  108  defined by the first heating element  102 . The subsequent reference temperature voltage  134  can be the same as, or different from, such as being lower than or greater than, the first reference temperature voltage  114 . The at least one subsequent temperature feedback voltage  132  can be the same as, or different from, such as being lower than or greater than, the first temperature feedback voltage  120 . The at least one subsequent output voltage, and any subsequent output voltage, can be the same as, or different from, such as being lower than or greater than, the first output voltage  120 . 
     Referring to  FIGS.  1  - 3   , the first diode  112  can be located within the target area to be heated by the heating element  102 . The first diode  112  functions as a temperature sensor, and the first temperature feedback voltage  116  sent by the first diode  112  provides information regarding the temperature within the target area to the first operational transconductance amplifier  110 . In examples where the heating element  102  defines a closed boundary, the first diode  112  can be located within the closed boundary  104 . Referring to  FIG.  3   , in at least some such examples, the first diode  112  can be located centrally within the closed boundary  104 , such as being equidistant, or substantially equidistant, from at least two opposing sides of the closed boundary  104 . For example, the first diode  112  can be equidistant, or substantially equidistant, from a first set of opposing sides of the closed boundary  108  defined by the heating element  102 , such as first side  122  and second side  124 . As further shown in  FIG.  3   , the first diode  112  can also be equidistant, or substantially equidistant, from a second set  126  and  128  of opposing sides of the closed boundary  108  defined by the heating element  102 , such as third side  126  and fourth side  128 . 
     Referring to  FIGS.  4  and  5   , the first heating element  102  and the components of the first regulation loop  104 , including the first operational transconductance amplifier  110  and the first diode  112  as shown in  FIG.  1   , can all be located on the chip  200 . It should be understood that systems on a chip (SoCs), such as chip  200 , can include any number of other devices on the chip  200  that are part of the SoC. Referring to  FIG.  3   , in addition to the first diode  112 , any SoC devices that are desired to be influenced by the first heating element  102 , such as reference voltage  202  and temperature sensor  204 , can be placed inside the target area  118 . 
       FIGS.  4  and  5    illustrate alternative examples for the location of the reference voltage  106 .  FIG.  4    shows an example in which the reference voltage  106  is located on the chip  200 . In such examples, the reference voltage  106  can be provided in any suitable manner, such as being part of an on-chip, temperature insensitive, digital to analog converter (DAC) system. In addition, when the reference voltage  106  is located on the chip  200 , the temperature control loop  104  can be enabled during normal operation of the SoC in cases where temperature regulation is desired, which may reduce the operation temperature range. 
       FIG.  5    shows an example in which the reference voltage  106  is provided external to the chip  200 , and is thus not located on the chip  200 . In such examples, the reference voltage  106  can be supplied in any suitable manner, including by external equipment, such as lab equipment or a production test system. 
     Referring back to  FIGS.  1  and  2   , the components of the programmable temperature regulation circuit  100  can be powered by a plurality of power sources. In at least some examples, a first power supply  130  having a first voltage supplies power to the components of the first regulation loop  104 , including the first diode  112  and the first operational transconductance amplifier  110 . The first power supply  130  can be a low voltage power supply, such as having a voltage that is less than or equal to about 5 volts, or between about 2 volts and about 5 volts. A second power supply  132  having a second voltage can be used to supply power to the first heating element  102 . The first voltage of the first power supply  130  can be lower than the second voltage of the second power supply  132 . In at least some examples, the second power supply  132  may have a voltage of up to about 90 volts, or up to about 100 volts, or potentially higher than 90 volts, including higher than 100 volts. In at least one example, the second power supply  132  can be an external power supply, not provided on the chip. Use of a higher voltage power supply for the second power supply  132  may provide increased energy efficiency, and may allow a flexible choice of power heating device and heating voltage without changing the power supply or needs of the components of the first regulation loop  104 . 
       FIG.  6    is a flow chart showing one method  300  of operating a programmable temperature regulation circuit of the present technology, such as programmable temperature regulation circuit  100  as shown in  FIGS.  1 - 5   , or programmable temperature regulation circuit  400 , shown in  FIG.  6    (discussed further below). 
     The method  300  starts at step  302 , which includes providing a fist regulation loop operatively connected to a first heating element, such as heating element, on a chip. The first regulation loop includes a first diode and a first operational transconductance amplifier. The first diode, such as first diode  112  in  FIG.  1   , has a negative temperature coefficient, meaning that as the temperature inside the target area increases, the voltage across first diode will decrease. 
     Referring back to  FIG.  6   , the method proceeds to step  304 , which includes providing a reference temperature voltage from a reference voltage to the first operational transconductance amplifier. As shown in  FIGS.  4  and  5   , the reference voltage  106  can be provided on the chip or external to the chip, depending upon the application. 
     Referring back to  FIG.  6   , the method can proceed to step  306 , which includes providing a first temperature feedback voltage from the first diode to the first operational transconductance amplifier. The first temperature feedback voltage, such as first temperature feedback voltage  116  in  FIG.  1   , relates to the temperature measured by the first diode  112  at a first point in time, which may be an initial temperature in the target area. Additionally, while step  306  is provided in  FIG.  6    after step  304 , they can occur in any order, simultaneously, or substantially simultaneously. Referring to  FIG.  1   , the first reference temperature voltage  114  and first temperature feedback voltage  116  are provided as inputs to control the first operational transconductance amplifier  110 . Generally, if a higher temperature in the target area  118  is desired, the first reference temperature voltage  114  should be lower than the first temperature feedback voltage  116 . 
     Referring back to  FIG.  6   , the method can proceed to step  308 , which includes generating by the first operational transconductance amplifier (OTA) a first output voltage based at least in part on the first temperature feedback voltage and the reference temperature. Referring to  FIG.  1   , the first operational transconductance amplifier  110  generates a first output voltage  120  based at least in part on the first temperature feedback voltage  116  and the reference temperature voltage  114 . If the first temperature feedback voltage  116  is higher than the reference temperature voltage  114 , the first operational transconductance amplifier  110  will generate a first output voltage  120 . 
     Referring back to  FIG.  6   , the method can proceed to step  310 , which includes providing a first amount of electrical power from the regulation loop to the first heating element. For example, the first output voltage  120  from the first operational transconductance amplifier  110  can cause a first amount of electrical power to be provided to the heating element  102  from the power supply for the heating element  102 , such as the second power supply  132 . 
     Referring back to  FIG.  6   , the method can proceed to step  312 , which includes converting the first amount of electrical power to heat using the first heating element on the chip. In other words, referring to  FIG.  1   , the heating element can receive a first amount of power from the second power supply  132 , and convert that power to heat that is used to heat the target area  118 . 
     The method  300  can include repeating steps  306 - 312  at least a second time, or periodically or continuously, in order to adjust, maintain, or otherwise control the amount of heat being generated by the first heating element  102 . For example, referring to  FIGS.  1  and  2   , when the heating element  102  provides heat to the target area  118  in response to the first output voltage  120  generated by the first operational transconductance amplifier  110 , the voltage across the first diode  112  will decrease, and the subsequent temperature feedback voltage  132  provided by the fist diode  112  will be decreased. Even assuming the subsequent reference temperature voltage  134  from the reference voltage  106  does not change, and is equal to the first reference temperature voltage  114 , the subsequent output voltage  136  would differ from the first output voltage  120  due to the change in the temperature feedback voltage from the first diode  112 . If the subsequent temperature feedback voltage  132  from the first diode  112  equals the subsequent reference temperature voltage  134 , the subsequent output voltage  136  from the first operational transconductance amplifier  110  can be an amount that is just sufficient to maintain the temperature feedback voltage from the first diode  112  at the same level as the reference temperature voltage. This may provide temperature stability for at least the first diode  112  and the SoC devices within the target area  118 . 
     The present disclosure is intended to encompass numerous additional embodiments including those disclosed herein as well as a variety of alternate embodiments. For example, as shown in  FIG.  7   , a programmable temperature regulation circuit  400  of the present technology can include a plurality of heating elements and an associated plurality of regulation loops provided on a single chip  402 . The heating elements and regulation loops can be operated in conjunction with one another, such as being operated simultaneously, to provide heating of one or more target areas, such as target area  404 , on the chip  402 . Accordingly, in addition to the first heating element, first operational transconductance amplifier, and first diode, a programmable temperature regulation circuit of the present technology can include at least a second heating element on the chip that converts a second amount of electrical power to heat, a second operational transconductance amplifier, and a second diode that provides a second temperature feedback voltage to the second operational transconductance amplifier. It should be understood that, while four heating elements, and their associated regulation loops, are shown in  FIG.  7   , any suitable number could be used depending upon the configuration of the particular SoC system with which the programmable temperature regulation circuit is being used. 
     As shown in  FIG.  7   , the programmable temperature regulation circuit  400  includes a first heating element  408 , a second heating element  410 , a third heating element  412 , and a fourth heating element  414 . The programmable temperature regulation circuit  400  includes a first regulation loop, which includes first operational transconductance amplifier  416  and a first diode  418 , which is operatively connected to the first heating element  408 . The programmable temperature regulation circuit  400  can also include a second regulation loop, which includes second operational transconductance amplifier  420  and a second diode  422 , which is operatively connected to the second heating element  410 . The programmable temperature regulation circuit  400  can further include a third regulation loop, which includes third operational transconductance amplifier  424  and a third diode  426 , which is operatively connected to the third heating element  412 . The programmable temperature regulation circuit  400  can further include a third regulation loop, which includes fourth operational transconductance amplifier  428  and a fourth diode  430 , which is operatively connected to the fourth heating element  414 . 
     The programmable temperature regulation circuit  400  further includes at least one reference voltage  406 , which can provide a reference temperature voltage  432  to each of the operational transconductance amplifiers, including first operational transconductance amplifier  416 , second operational transconductance amplifier  420 , third operational transconductance amplifier  424 , and fourth operational transconductance amplifier  428 . As with reference voltage  106  of the programmable temperature regulation circuit  100 , reference voltage  406  can be provided on the chip  402  or external to the chip  402 . 
     During operation, each operational transconductance amplifier receives a temperature feedback voltage from the diode operatively connected thereto, and the reference temperature voltage from the reference voltage, and generates an output voltage based at least in part on the first temperature feedback voltage and the reference temperature voltage. The first output voltage generated by each operational transconductance amplifier controls an amount of electrical power provided to the heating element operatively connected thereto. Each heating element converts the received amount of electrical power to heat, and provides the heat to the target area. 
     Accordingly, in the example illustrated in  FIG.  7   , the first operational transconductance amplifier  416  receives the first temperature feedback voltage  434  from the first diode  418  and the reference temperature voltage  432  from the reference voltage  406 , and generates a first output voltage  436  based at least in part on the first temperature feedback voltage  434  and the reference temperature voltage  432 . The first output voltage  436  generated by the first operational transconductance amplifier  416  controls a first amount of electrical power provided to the first heating element  408 . The first heating element  408  converts the first amount of electrical power to heat, and provides that heat to the target area  404 . Additionally, the second operational transconductance amplifier  420  receives the second temperature feedback voltage  438  from the second diode  422  and the reference temperature voltage  432  from the reference voltage  406 , and generates a second output voltage  440  based at least in part on the second temperature feedback voltage  438  and the reference temperature voltage  432 . The second output voltage  440  generated by the second operational transconductance amplifier  420  controls a second amount of electrical power provided to the second heating element  410 . The second heating element  410  converts the second amount of electrical power to heat, and provides that heat to the target area  404 . Further, the third operational transconductance amplifier  424  receives the third temperature feedback voltage  442  from the third diode  426  and the reference temperature voltage  432  from the reference voltage  406 , and generates a third output voltage  444  based at least in part on the third temperature feedback voltage  442  and the reference temperature voltage  432 . The third output voltage  444  generated by the third operational transconductance amplifier  424  controls a third amount of electrical power provided to the third heating element  412 . The third heating element  412  converts the third amount of electrical power to heat, and provides that heat to the target area  404 . Finally, the fourth operational transconductance amplifier  428  receives the fourth temperature feedback voltage  446  from the fourth diode  430  and the reference temperature voltage  432  from the reference voltage  406 , and generates a fourth output voltage  448  based at least in part on the fourth temperature feedback voltage  446  and the reference temperature voltage  432 . The fourth output voltage  448  generated by the fourth operational transconductance amplifier  428  controls a fourth amount of electrical power provided to the fourth heating element  414 . The fourth heating element  414  converts the fourth amount of electrical power to heat, and provides that heat to the target area  404 . 
     In accordance with the foregoing, in at least some embodiments encompassed herein, the present disclosure relates to programmable temperature regulation circuits, and methods of operating programmable temperature regulation circuits, for providing heat to a target area on a chip. 
     In one aspect, an example of a programmable temperature regulation circuit for providing heat to a target area on a chip is provided that can include a first heating element on the chip that converts a first amount of electrical power to heat. The programmable temperature regulation circuit can also include a first regulation loop operatively connected to the heating element, wherein the first regulation loop controls provision of the first amount of electrical power to the first heating element, the first regulation loop including a first operational transconductance amplifier that receives, at a first point in time, a first reference temperature voltage and a first temperature feedback voltage, and a first diode that provides the first temperature feedback voltage to the first operational transconductance amplifier. The programmable temperature regulation circuit can also include a reference voltage that provides the first reference temperature voltage to the first operational transconductance amplifier. 
     The first operational transconductance amplifier of the programmable temperature regulation circuit can generate a first output voltage based at least in part on the first temperature feedback voltage and the first reference temperature, and the first output voltage controls the provision of the first amount of electrical power to the first heating element. 
     The first heating element of the programmable temperature regulation circuit can be a transistor. 
     The first heating element of the programmable temperature regulation circuit can be selected from the group consisting of an n-channel metal-oxide semiconductor (NMOS) transistor, a P-channel metal—oxide semiconductor (PMOS) transistor, and a bipolar transistor. 
     The first heating element of the programmable temperature regulation circuit can define a closed boundary. In at least one example, the closed boundary is symmetrical in shape. Additionally, the first diode of the programmable temperature regulation circuit can be located on the chip within the closed boundary. For example, the first diode can be equidistant from a first side and a second side of a set of opposing sides of the closed boundary. 
     In an example, the first operational transconductance amplifier of the programmable temperature regulation circuit can generate a first output voltage based at least in part on the first temperature feedback voltage and the first reference temperature, and the first output voltage can control the provision of the first amount of electrical power to the first heating element. 
     The programmable temperature regulation circuit can include a first power supply having a first voltage that supplies power to the first diode and the first operational transconductance amplifier, and a second power supply having a second voltage that supplies power to the first heating element. In at least some examples, the first voltage is lower than the second voltage. For example, the first voltage can be less than or equal to 5 volts. In contrast, the second voltage can be up to about 100 volts. 
     The reference voltage of the programmable temperature regulation circuit can be located on the chip. Alternatively, the reference voltage of the programmable temperature regulation circuit can be external to the chip. 
     At a second point in time, the first operational transconductance amplifier of the programmable temperature regulation circuit can receive a subsequent reference temperature voltage from the reference voltage and a subsequent temperature feedback voltage from the first diode. The first operational transconductance amplifier can generate a subsequent output voltage based at least in part on the subsequent temperature feedback voltage and the subsequent reference temperature. 
     The programmable temperature regulation circuit can further comprise a second heating element on the chip that converts a second amount of electrical power to heat; a second operational transconductance amplifier; and a second diode that provides a second temperature feedback voltage to the second operational transconductance amplifier. The second operational transconductance amplifier can receive the second temperature feedback voltage from the second diode and the reference temperature from the reference voltage, and can generate a second output voltage based at least in part on the second temperature feedback voltage and the reference temperature. The second output voltage can control the second amount of electrical power provided to the second heating element. 
     In another aspect, an example of a method of operating a programmable temperature regulation circuit to heat a target area is provided. The method can include providing a first regulation loop operatively connected to a first heating element on a chip, the first regulation loop including a first diode and a first operational transconductance amplifier. The method can also include providing a first temperature feedback voltage from the first diode to the first operational transconductance amplifier, and providing a reference temperature voltage from a reference voltage to the first operational transconductance amplifier. The method can further include providing a first amount of electrical power to the first heating element. 
     In an example, the method can include generating by the first operational transconductance amplifier a first output voltage based at least in part on the first temperature feedback voltage and the reference temperature. In an example, the method can also include converting the first amount of electrical power to heat using the first heating element on the chip. 
     One or more of the embodiments encompassed herein can be advantageous in any of a variety of respects. For example, programmable temperature regulation circuits as described herein may provide lower testing costs. Additionally, programmable temperature regulation circuits as described herein may allow regulation of the operating temperature of temperature sensitive components on the chip, which may provide improved accuracy in performance over the whole operating temperature range. Further, use of an external power source as the power supply for the heating element(s) can allow increased efficiency by reducing the heating current and time duration for the same temperature change. 
     While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention. It is specifically intended that the present invention not be limited to the embodiments, examples, and illustrations contained herein, but include modified forms of those embodiments and examples including portions of the embodiments and examples, and combinations of elements of different embodiments and examples as come within the scope of the following claims.