PATENT DOCUMENT

Publication Number: US-8182139-B2
Application Number: US-13065008-A
Country: US
Kind Code: B2

Title: Calibration of temperature sensing circuitry in an electronic device

Abstract:
Temperature sensing circuitry is used for thermal management of an electronic device. The temperature sensing circuitry includes at least one thermistor placed at or near a component of the electronic device. The temperature sensing circuitry also includes a high-precision resistor for calibration purposes. The resistance of the resistor is equivalent to the resistance of the thermistor at a reference temperature. A calibration reading is obtained using a set current that is being passed through the resistor. An error present in the temperature sensing circuitry is determined based on the calibration reading and a design value. A temperature measurement associated with the component is then made using the thermistor, while the set current is being passed through the thermistor. The error is corrected in the temperature measurement of the component. Other embodiments are also described.

Claims:
1. A method for thermal management in an electronic device, comprising:
 obtaining a calibration reading using a set current that is being passed through a resistor in a temperature sensing circuit, wherein the temperature sensing circuit includes a thermistor which is placed at or near a component of the electronic device and the resistance of the resistor is equivalent to the resistance of the thermistor at a reference temperature; 
 determining an error present in the temperature sensing circuit based on the calibration reading and a design value; and 
 correcting for the error in a temperature measurement associated with the component, wherein the measurement is made using the thermistor while the set current is being passed through the thermistor. 
 
     
     
       2. The method of  claim 1 , wherein determining an error present in the temperature sensing circuit further comprises:
 determining error in an analog-to-digital converter (ADC) and a current generator in the temperature sensing circuit, wherein the current generator provides the set current. 
 
     
     
       3. The method of  claim 1 , wherein the design value is based on a manufacture or design specification of an ADC, a current source, and the resistor in the temperature sensing circuit. 
     
     
       4. The method of  claim 1 , wherein the resistor is more accurate than the thermistor. 
     
     
       5. The method of  claim 1 , wherein the resistor is accurate to within +/−0.1% or better, and the thermistor is accurate to within +/−1% or better. 
     
     
       6. An apparatus for thermal management in an electronic device, the apparatus comprising:
 means for providing a set current; 
 means for alternately passing the set current through a resistor and a thermistor wherein the resistance of the resistor equivalent to the resistance of the thermistor at a reference temperature; 
 means for obtaining a digital calibration reading while the set current is being passed through the resistor; 
 means for obtaining digital thermistor reading while the set current is being passed through the thermistor; 
 means for computing an error based on the digital calibration reading and a design value; and 
 means for providing a corrected temperature measurement, based on the computed error and the digital thermistor reading. 
 
     
     
       7. An apparatus for thermal management in an electronic device, comprising:
 a current generator to provide a set current; 
 a multiplexer having an input coupled to receive the set current; 
 a thermistor coupled to an output of the multiplexer; 
 a resistor coupled to another output of the multiplexer, the resistor having a resistance that is equivalent to a resistance of the thermistor at a reference temperature; 
 an analog-to-digital converter (ADC) coupled to the input of the multiplexer, to obtain a digital thermistor voltage using the thermistor while the set current is being passed through the thermistor and a digital calibration reading using the resistor while the set current is being passed through the resistor; 
 a processing circuit to receive the thermistor voltage and the calibration reading, compute an error based on the calibration reading and a design value, and correct a temperature measurement based on the error and the thermistor voltage. 
 
     
     
       8. The apparatus of  claim 7 , wherein the processing circuit is to correct a temperature measurement by converting a corrected voltage measurement into a temperature value. 
     
     
       9. The apparatus of  claim 7 , wherein the design value is based on a manufacture or design specification of the ADC, the current generator, and the resistor. 
     
     
       10. The apparatus of  claim 7 , wherein the resistor is more accurate than the thermistor. 
     
     
       11. A method for thermal management in an electronic device, comprising:
 obtaining a digitized resistor voltage while a set current provided by a current source is being passed through a resistor in a temperature sensing circuit, wherein the temperature sensing circuit includes a thermistor which is placed at or near a component of the electronic device and the resistance of the resistor is equivalent to the resistance of the thermistor at a reference temperature; 
 computing an error present in the temperature sensing circuit based on the digitized resistor voltage and a design value; 
 obtaining a digitized thermistor voltage while the set current provided by the current source is being passed through the thermistor; and 
 correcting a temperature measurement associated the component, based on the computed error and the digitized thermistor voltage. 
 
     
     
       12. The method of  claim 11 , wherein correcting comprises converting a corrected voltage measurement into a temperature value. 
     
     
       13. The method of  claim 11 , wherein the design value is based on a manufacture or design specification of an ADC that was used for obtaining the digitized resistor and thermistor voltages, the current source, and the resistor in the temperature sensing circuit. 
     
     
       14. The method of  claim 11 , wherein the resistor is more accurate than the thermistor.

Description:
TECHNICAL FIELD 
     An embodiment of the invention relates generally to thermal management, and more particularly, to a temperature sensing system in a portable electronic device. Other embodiments are also described. 
     BACKGROUND 
     Portable electronic devices are becoming increasingly popular. Examples of portable electronic devices include laptop computers, personal digital assistants (PDAs), mobile telephones, media players, and hybrid devices that provide a combination of the functionalities of the above devices. 
     To satisfy consumer demand for small and lightweight portable electronic devices, manufacturers are continually striving to reduce the size of the devices while providing enhanced functionality. When electronic components are tightly packaged in a small device, heat dissipation becomes an important issue. As most consumer electronics cannot function properly at a high temperature for an extended period of time, manufacturers often place temperature sensors, such as thermistors, to monitor the internal temperature of the electronic devices. These temperature sensors allow out of range temperature scenarios to be recognized, so that mitigation actions can be taken before system failure. 
     Conventionally, temperature sensors in a device are calibrated to ensure their accuracy, by heating up the device to a known temperature. The output of the temperature sensors is then compared with an expected temperature to determine an error in the sensor output. This error is then stored in the device for later use. Thereafter, the device, while being used “in the field”, then automatically compensates the readings from its sensors using the stored error values. However, the conventional calibration process requires heating up the motherboard of a device in an oven, which is a complex process in terms of time and resources. Further, the conventional calibration process cannot be performed in the field, i.e. after the devices have been packaged and shipped by its manufacturer for resale. 
     SUMMARY 
     Temperature sensing circuitry is used for thermal management of an electronic device. As modern electronic devices often operate near hot limits to maximize performance, the temperature measurements taken using the sensing circuitry in every manufactured device should be accurate, to ensure that the hot limit is never exceeded and that the performance of the device is not unduly lowered. Reliable and low cost calibration of the temperature sensing circuitry is thus needed. 
     In one aspect of the invention, the temperature sensing circuitry includes at least one thermistor placed at or near a component of the electronic device. The temperature sensing circuitry also includes a high-precision resistor for calibration purposes. The resistance of the resistor is equivalent to the resistance of the thermistor at a reference temperature. A calibration reading is obtained using a set current that is being passed through the resistor. An error present in the temperature sensing circuitry is determined, based on the calibration reading and its design value. A temperature measurement associated with the component is then made using the thermistor, while the set current is being passed through the thermistor. The determined error is applied to correct the temperature measurement of the component. Other embodiments of the invention are also described below. 
     Embodiments of the present invention include apparatuses and data processing systems which perform these methods, and computer readable media which when executed by data processing systems cause the systems to perform these methods. 
     Other features of the present invention will be apparent from the accompanying drawings and from the detailed description which follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  is a diagram of illustrative temperature sensing circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of an illustrative temperature coefficient curve of a thermistor used in the temperature sensing circuitry in accordance with an embodiment of the present invention. 
         FIG. 3  is flow diagram of an illustrative process for calibrating the temperature sensing circuitry in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram of an illustrative wireless electronic device in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention. Numerous specific details are described to provide a thorough understanding of the present invention. However, in certain instances, well known or conventional details are not described in order to avoid obscuring the description of the present invention. References to one or an embodiment in the present disclosure are not necessarily references to the same embodiment; and, such references mean at least one. 
     An electronic computing device typically generates heat in operation. After a period of operation, the temperature of the device may rise to a level that causes damage to its internal electronics—a so-called hot limit. To prevent heat damage, power settings of one or more of the device components can be dynamically adjusted based on the temperature of the components. The adjustment in power settings reduces power consumption, which, in turn, reduces the temperature of the device. 
     In one embodiment, the electronic computing device includes a temperature sensing subsystem to monitor the temperatures of its components. These components may be a heating generating component, a component sensitive to high temperature, a component near a heat source, a component distant from the main heat generating components, or other components that are good indicators of internal, external, or ambient temperatures of the device. 
     In one embodiment of the present invention, it is recognized that a temperature sensing subsystem can be calibrated with a high-precision resistor. The resistor is chosen to have the equivalent resistance of a thermistor at a reference temperature that is below the upper temperature limit of the system. In one embodiment, the reference temperature can be chosen to be in the proximity of the desired operating temperature of the system, which is near the hot limit. 
       FIG. 1  is a simplified block diagram of an embodiment of temperature sensing circuitry  180  deployed within an electronic computing device  100 . Temperature sensing circuitry  180  includes one or more thermistors  112 - 114  and a resistor  110 , all of which are coupled to a thermal monitor  135  via a plurality of I/O pins  165 . In one embodiment, thermal monitor  135  may be part of a single-chip circuit module  160 , such as a cellular baseband processor integrated circuit package, in a wireless communication device. Resistor  100  is external to the integrated circuit package, and may be coupled to an unused thermistor input pin of the integrated circuit package. For simplicity of illustration, resistor  110  is shown as located next to thermistors  112 - 114 . However, resistor  110  may be located anywhere in device  100 , and may not be located next to or near thermistors  112 - 114 . 
     Thermal monitor  135  includes a multiplexer  120 , the output of which is coupled to a current source  130  and an analog to digital converter (ADC)  140 . Current source  130  supplies a set current to drive a resistive load in the temperature sensing circuitry  180 , thereby providing a voltage at the output of multiplexer  120  (i.e., at a point  170 ). ADC  140  converts the voltage at point  170  into a digital measurement. Electronic computing device  100  uses the digital measurements to monitor the temperatures of its components, such that power consumption may be dynamically adjusted, thereby preventing damage to the electronics caused by excessive heat. 
     In one embodiment, each of the thermistors  112 - 114  is placed near or at a component of electronic computing device  100  to measure the temperature of the component. In an embodiment where electronic computing device  100  is a handheld wireless communication device, the components for which the temperatures are measured may include a battery, a RF transmitter power amplifier, a subscriber identity module (SIM) card circuit, and other electronic modules. The SIM card circuit in a handheld device is generally located away from the main heat generating components; therefore, the temperature reading at the SIM card circuit provides a thermal reading that is distant from the main heat generating components and can be used to monitor the ambient temperature of the device. Temperatures may also be monitored at or near non-electrical parts of the system for user satisfaction (e.g., to prevent a handheld device from overheating to cause user discomfort). The non-electrical parts may include the portion of the housing at the earpiece (receiver), and the center of the housing&#39;s back panel. 
       FIG. 2  illustrates the temperature-resistance curve  200  of an example thermistor  112 - 114 . Temperature-resistance curve  200  is also referred to as a negative temperature coefficient (NTC) curve, as the resistance drops when the temperature increases. In one embodiment, a critical thermal bound  210  of electronic computing device  100  is the upper bound of temperatures for which the operation of device  100  is optimized. Critical thermal bound  210  is near but below a hot limit of the device. For example, critical thermal bound  210  may be determined based on the safety limit of the battery in device  100 , a customer satisfaction limit, and other factors. Device  100  may operate below critical thermal bound  210  with little or no performance impact caused by the thermal management. When the temperature of device  100  rises to a point where it is likely to exceed critical thermal bound  210 , thermal mitigation actions may be initiated to reduce the power consumption of device  100 . Thus, the critical thermal bound  210  may be a relatively narrow range of temperatures, e.g. at about 60 degrees +/− less than 2 degrees. 
     A reference temperature  220  is chosen near or in critical thermal bound  210 . Reference temperature  220  can be used to select the resistance of resistor  110 . In one embodiment, the resistance of resistor  110  is chosen such that it is equivalent to the resistance of thermistors  112 - 114  at reference temperature  220 . Thus, the point representing the resistance of resistor  110  and reference temperature  200  falls on the temperature-resistance curve. Resistor  110  is a precision resistor that for example may be accurate to within approximately 0.1% or better. That is, the actual resistance of resistor  110  may be guaranteed by its manufacturer to be within approximately 0.1% of the design (or theoretical) resistance value, or better. In comparison, thermistors  112 - 114  may be substantially less accurate, e.g., accurate within approximately 1% of the design value. In one embodiment, the precision resistor has an accuracy or tolerance at least an order of magnitude (factor of 10) better than that of the thermistors  112 - 114 . 
     Referring again to  FIG. 1 , during operation of temperature sensing circuitry  180 , multiplexer  120  selects one of resistor  110  and thermistors  112 - 114  according to a selection signal  150 . Selection signal  150  may be generated by a user command, a software-generated command, or circuitry that resides within or outside of circuit module  160 . When one of the thermistors  112 - 114  is selected, multiplexer  120  establishes a current path from the selected thermistor to ADC  140 . The current supplied by current source  130  passes through multiplexer  120  and the selected thermistor to establish a voltage at the input of ADC  140 , which is converted to a digital measurement by ADC  140 . The digital measurement can be converted to a temperature according to a predetermined conversion table or a conversion formula. 
     However, the digital measurement may deviate from the true temperature value in device  100  due to the inaccuracy in thermistors  112 - 114 , current source  130 , ADC  140 , as well as any other components in the measurement path. For example, thermistors  112 - 114  may each have about 1% of inaccuracy. Additionally, current source  130  and ADC  140  may each have about 2% of inaccuracy. The inaccuracy of these circuit elements may accumulate to produce a temperature measurement that is below or above the true temperature value, by in this example 5%. In many instances, this may be too large a margin, because many specimens of the device  100  will, as a result, be operating less efficiently in the field. To explain, consider the following example. 
     With +/−5% total inaccuracy, the thermal management system may have a “programmed hot limit” that is 5% less than the actual hot limit. This helps ensure that every manufactured device will be in compliance of the actual hot limit, despite some devices reading low and others high. Now, while the low devices may indicate the temperature to be as low as 55 degrees, the high devices will indicate as high as 65 degrees, even when the actual temperature is 60 degrees. But due to the inaccuracy, the thermal management system running in the high devices may have to reduce performance when the actual temperature is only about 50 degrees, almost a full ten degrees below the actual limit. As a result, consumers who have by chance been given high devices may be experiencing noticeably lower performance levels than others who have low devices. Calibration may help reduce the total inaccuracy of the temperature sensing capability. 
     To calibrate the circuit elements in temperature sensing circuitry  180 , multiplier  120  selects resistor  110  to establish a path between resistor  110  and ADC  140 . The set current supplied by current source  130  flows through resistor  110  to provide a voltage at the input of ADC  140 . In one embodiment, resistor  110  has a resistance that is the equivalent to the resistance of thermistors  112 - 114  at the reference temperature, e.g., between about 55 to 60 degrees centigrade, depending on the type of electronics used in the electronic computing device  100 . 
     When resistor  110  is used, the digital measurement at the output of ADC  140  includes an error present in resistor  110 , current source  130  and ADC  140 . As current source  130  and ADC  140  are far less accurate than resistor  110 , the inaccuracy of resistor  110  may be negligible in the resulting digital measurement. For example, if resistor  110  has the same resistance as a thermistor  112 - 114  at 60 degrees centigrade, the ADC output per manufacturer or design specification may be, illustratively, 1000 (before conversion into a temperature). However, due to the errors introduced by current source  130  and ADC  140 , the actual digital measurement may be, illustratively, 980. The 20 units of difference can be used to calibrate temperature sensing circuitry  180  in order to remove the errors introduced by current source  130  and ADC  140 . A process for calibrating temperature sensing circuitry  180  is described in greater detail with reference to  FIG. 3  below. 
       FIG. 3  is a flow diagram of an embodiment of a process  300  for calibrating temperature sensing circuitry  180  of  FIG. 1 . Process  300  may be implemented with software, firmware, and/or hardware in electronic computing device  100 . In one embodiment, process  300  may be executed by circuit module  160  of  FIG. 1 , a processor of electronic computing device  100 , or other processing circuits of electronic computing device  100 . 
     Referring to  FIG. 3 , a calibration baseline is established by using resistor  110  of  FIG. 1 . At block  310 , in response to selection signal  150 , multiplexer  120  establishes a current path through the resistor  110 . At block  320 , the output of ADC  140  is recorded in local storage as a calibration measurement. At block  330 , the calibration measurement is compared with a design value to compute an error. The design value is based on the manufacture or design specification of ADC  140 , current source  130 , and resistor  110 . At block  340 , a thermistor measurement is taken (using the ADC  140 ) by selecting one of thermistors  112 - 114  and establishing the same current through the selected thermistor. At block  350 , the error is applied to the thermistor measurement to calculate a corrected measurement. At block  360 , the corrected measurement is converted into a temperature value using a conversion table or a conversion formula. The temperature value indicates the temperature of the component associated with the selected thermistor. As an alternative, the conversion of the thermistor measurement to the temperature value can be performed before applying the computed error to obtain the corrected measurement. That is, the conversion operation of block  360  may be performed on the error at block  330  and on the thermistor measurement at block  340 . The converted error can then be applied to the converted thermistor measurement to obtain a corrected temperature value. 
     The temperature value may be further processed by software run by circuit module  160  or other software/hardware modules in electronic computing device  100 . At block  370 , the temperature value is compared to a predefined threshold temperature. Based on the comparison result, at block  380 , power consumption of electronic computing device  100  may be increased or decreased to adjust the temperature in device  100 . In one embodiment, power consumption may be managed by a separate circuit module in device  100 , such as a power management unit. An embodiment of a power management unit will be described with reference to  FIG. 4 . 
     A feature of process  300  is that it can be performed at any time of the lifecycle of the electronic computing device  100 , for as many times as necessary. The calibration measurement using resistor  110  may be read every time the temperatures of device components are measured. Process  300  does not involve heating up device  100  in an oven, which is a complex process in terms of time and resources. 
     In one embodiment, the electronic computing device  100  of  FIG. 1  may be a portable electronic device, as that is where the benefits of the invention will be most apparent. However, the invention could if desired be implemented in a desktop personal computer, for instance. The portable electronic device may be a laptop computer, a handheld electronic device (such as a personal digital assistant or a handheld gaming device), a media player, or a wearable electronic device. Examples of wearable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. In some embodiments, the portable electronic device may be provided with wireless communication capability, such as cellular telephones, cordless telephones, remote controllers and global positioning system (GPS) devices. The wireless electronic devices may be hybrid portable electronic devices that combine the functionality of multiple conventional devices. Examples of hybrid portable electronic devices include a cellular telephone that includes media player functionality, a gaming device that includes wireless communications capability, a cellular telephone that includes game and email functions, and a portable device that receives email, supports mobile telephone calls, has music player functionality and supports web browsing. These are merely illustrative examples. 
     In one embodiment, the portable electronic device may include circuitry to run software applications, such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. The portable electronic device may also be used to implement communications protocols, such as Internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols, also known as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, protocols for handling 3G communications services, 2G cellular telephone communications protocols, etc. The term “2G communications” herein refers to traditional cellular telephone and data communications. An example of 2G cellular telephone systems are those based on Global System for Mobile Communication (GSM) systems. The term “3G communications” herein refers to communications with newer formats that support increased speeds and may be used for both data and voice traffic. Such formats may use wide band code-division multiple access (CDMA) technology. In some embodiments, wireless signals can also be sent using light (e.g., using infrared communications). 
     In accordance with an embodiment of the present invention, an illustrative portable electronic device  400  with wireless communications capability is shown in  FIG. 4 . It is understood that for clarity of the description, components of portable electronic device  400  that are not germane to this disclosure are not described. 
     As shown in  FIG. 4 , portable electronic device  400  includes a processor  450 , which serves as the main processor for implementing user functions. In this capacity, processor  450  may be used to run applications for the user such as media playback applications, communications applications, calendar applications, games, notepad applications, business applications, etc. 
     The operations of processor  450  may be supported using a memory  460  that comprises one or more memory modules. Memory  460  may include a relatively small memory module (e.g., 8 Mbytes) that is used to store boot instructions. Memory  460  may also include a larger memory module (e.g., 4-16 Gbytes) that is used to store applications and data, and a static Random Access Memory (RAM) for fast memory operations. Memory  460  may include nonvolatile and volatile memory modules. 
     Device  400  also includes a baseband processor  452  to provide data processing function for the data received and the data to be transmitted. Baseband processor  452  may receive data from processor  450 , audio data from an audio codec  414 , GPS data from an antenna  462 , or other sources. 
     Baseband processor  452  may, if desired, be implemented as a single integrated circuit. Baseband processor  452  may provide data to be transmitted to transceiver  454  (e.g., radio frequency (RF) transceiver circuitry that can handle 2G operations and that can handle 3G operations using wide band code division multiple access techniques). Baseband processor  52  may be coupled to power amplifier circuitry  456  (e.g., 2G GSM power amplifier circuit and 3G power amplifier circuitry). Memory  404  may be used to store data for baseband processor  452 . Memory  404  may be, for example, 8-16 MB of static random-access memory (SRAM). 
     Baseband processor  452  may include processing circuitry for handling audio signals. For example, baseband processor  452  may include a digital signal processor (DSP) block that performs functions such as noise suppression, gain control, filtering, analog-to-digital conversion, digital-to-analog conversion, and vocoding (e.g., functions such as compressing audio to phase-code-modulation-encoded signals for transmission over a wireless network, voice decoding functions, etc.). 
     Audio codec  414  may reside on a separate chip to handle telephony audio signals and other audio signals. For example, speakers and a microphone may be coupled to audio codec  414 . 
     Device  400  includes an antenna  462 , which may further include a pentaband cellular antenna and a dual band antenna. Illustratively, the pentaband antenna may be used to cover wireless bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz, and the dual band antenna may be used to handle 1575 MHz signals for GPS operations, 2.4 GHz signals for Bluetooth® operations, and 2.4 and 5.0 GHz for IEEE 802.11 operations and wireless local area network (WLAN) operations. 
     Device  400  may be powered by a battery  483 . During data transmission, power amplifier circuitry  456  may boost the output power of transmitted signals to a sufficiently high level to ensure adequate signal transmission. Battery  483  may be a lithium ion battery, a lithium polymer battery, or a battery of any other suitable type. Battery  483  may be rechargeable and may be removed by an end user as necessary (e.g., when it is desired to replace a fresh battery). 
     Device  400  may include a subscriber identity module (SIM) connector  458  and other ports  430 . SIM connector  458  may be used to receive a SIM card for authorizing cellular telephone services. When the SIM card is installed in device  400 , an authorized user may use device  400  for voice and data wireless communications (e.g., using the 3G or 2G capabilities of devices  400 ). 
     Ports  430  may include power jacks to recharge battery  483  from a direct current (DC) power supply. Ports  430  may also include data ports to exchange data with external components such as a personal computer or peripheral, audio-visual jacks to drive a headphone, a microphone, a speaker, a monitor, or other external audio-video equipment, a memory card slot, etc. Digital video output signals from processor  450  may be supplied to video digital-to-analog converter (DAC) circuit  434 . The resulting analog video signals may be supplied to ports  430 . 
     The functions of some or all of these components and the internal circuitry of device  400  can be controlled using an interface device such as a touch screen display. 
     A display  416  of the device  400  may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, or any other suitable display. The outermost surface of display  416  may be formed from one or more plastic or glass layers. If desired, touch screen functionality may be integrated into display  416  or may be provided using a separate touch pad device. 
     Device  400  may have other user interface devices  472 , such as buttons (e.g., alphanumeric keys, power on-off, power-on, power-off, and other specialized buttons, etc.), touch pads, key pads, keyboards, pointing sticks, click wheels, scrolling wheels, or other cursor control device, a microphone for supplying voice commands, a camera, or any other suitable interface for controlling device  400 . If desired, device  400  can be controlled remotely (e.g., using an infrared remote control, a radio-frequency remote control such as a Bluetooth® remote control, etc.). 
     Device  400  may include other I/O devices  473 , such as light-emitting diodes (LEDs) to visually display the status of device  400 , speakers to generate sounds, a vibrator to generate vibration during silent operations, etc. 
     In the embodiment shown in  FIG. 4 , thermal monitor  135  of temperature sensing circuitry  180  ( FIG. 1 ) resides in baseband processor  452 . For simplicity of the circuit diagram, thermistors  112 - 114  and resistor  110  are not shown in  FIG. 4 . Thermistors  112 - 114  may be placed near or at battery  483 , power amplifiers  456 , SIM connector  458 , or other components of device  400 . Resistor  110  may be located near baseband processor  452  or other convenient locations within device  400 . Thermal monitor  135  receives input signals from thermistors  112 - 114  and resistor  110 , and generates calibration measurements and temperature measurements. The temperature measurements, after calibration, may be used to manage the power consumption of device  400 . 
     To minimize power consumption, device  400  may include a power management unit  420  to implement power management functions. In response to the temperature measurement of thermistors  112 - 114  and thermal monitor  135 , power management unit  420  may adjust the power consumption by the components of device  400 , thereby maintaining the temperature of device  400  at or just below a critical thermal bound. Power management unit  420  reduces the power consumption to reduce heat generation when the temperature measurement exceeds the critical thermal bound threshold. When the temperature measurement drops below the threshold, power management unit  420  may increase the power supplied to that component and other components to improve performance. For example, power management unit  420  may adjust the gain settings of power amplifiers  456 , the voltages supplied by battery  483 , the backlight of display  416  or other visual output devices  473 , the voice/ data transmission rate and/or the processing speed of baseline processor  452 , as well as other functions of the device components. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Metadata:
Filing Date: 20080530
Publication Date: 20120522
Grant Date: 20120522
Priority Date: 20080530
Inventors: FIENNES HUGO
COX KEITH ALAN
Assignee: APPLE INC
CPC Classifications: [{"code": "G01K15/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01K7/425", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01K15/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01K7/425", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 41379756