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.

1 . An apparatus for thermal management in an electronic device, the apparatus comprising:
 integrated circuitry that includes an analog-to-digital converter (ADC), and a multiplexer having an output coupled to an input of the ADC;   a resistor coupled to a first input of the multiplexer; and   a thermistor coupled to a second input of the multiplexer, wherein the resistance of the resistor is about the same as the resistance of the thermistor when the thermistor is below a critical thermal bound of the electronic device.   
     
     
         2 . The apparatus of  claim 1 , further comprising:
 a current generator coupled between the ADC and the output of the multiplexer to provide a current to the resistor and the thermistor.   
     
     
         3 . The apparatus of  claim 1 , wherein the integrated circuitry is located in an integrated circuit package of a baseband processor for wireless communications. 
     
     
         4 . The apparatus of  claim 3 , wherein the resistor is coupled to a thermistor input pin of the integrated circuit package. 
     
     
         5 . The apparatus of  claim 1 , wherein the multiplexer receives input signals through a plurality of signal paths, each signal path to include a respective thermistor, where the respective thermistor is associated with one of the following components of the electronic device: a battery, an antenna power amplifier, and a subscriber identity module (SIM) card circuit. 
     
     
         6 . The apparatus of  claim 1 , wherein the thermistor is placed at or near a component of the electronic device to sense a temperature associated with the component. 
     
     
         7 . An article of manufacture comprising a computer readable medium including instructions that, when executed by a processing system, cause the processing system to:
 compute a temperature correction, based on an output signal of an analog-to-digital converter (ADC) while an input signal to the ADC is a function of a set current being passed through a resistor;   obtain a temperature reading, based on the output of the ADC while the input to the ADC is a function of the set current being passed through a thermistor; and   adjust the temperature reading with the temperature correction, to obtain a calibrated temperature that is associated with a component of the electronic device.   
     
     
         8 . The article of manufacture of  claim 7 , wherein the instructions cause the system to compute the temperature correction by
 obtaining a first temperature, based on the output signal of the ADC while the input signal to the ADC is a function of the set current through the resistor; and   computing a difference between the first temperature and a reference temperature, wherein the resistance of the resistor is about the same as the resistance of the thermistor when the thermistor is at the reference temperature.   
     
     
         9 . The article of manufacture of  claim 7 , wherein the instructions cause the system to treat the reference temperature as being below a critical thermal bound of the electronic device. 
     
     
         10 . The article of manufacture of  claim 9 , wherein the critical thermal bound is determined based on a safety limit of a battery and a customer satisfaction limit. 
     
     
         11 . The article of manufacture of claim of  claim 8 , wherein the resistance of the resistor and the reference temperature fall on a resistance-temperature curve of the thermistor.