Granted Patent B2

US 7,104,684 · App. 10/718,769 · Granted Sep 12, 2006

Assignee: Sigmatel, Inc.

Abstract

Claims (98)

1. A method for sensing a temperature of a device, that comprises:

establishing a programmable current for an on-chip current source;

sensing a temperature-dependent voltage that is based on a temperature dependent resistive component and the programmable current, wherein the temperature-dependent voltage is maintained within a predetermined range, and wherein the temperature dependent resistive component is thermally coupled to the device;

converting the temperature-dependant voltage to a digital value; and

equating the digital value to the temperature of the device.

2. The method of claim 1 further comprises adjusting the programmable current such that the temperature-dependent voltage is within a predetermined range of values for converting the temperature-dependent voltage into the digital value, wherein the equating of the digital value is further based on the adjusting of the programmable current.

3. The method of claim 1 , wherein the temperature dependent resistive component comprises a thermistor.

4. The method of claim 1 , wherein the equating the digital value to the temperature of the device further comprises determining the temperature of the device from a table relating digital values to temperatures.

5. The method of claim 1 , wherein the devices comprises an off-chip device, and wherein equating the digital value to the temperature of the off-chip device further comprises calculating the temperature of the off-chip device with a predetermined function wherein the temperature is a function of:

at least one property of the programmable current;

a digitized voltage; and

a set of physical properties of the temperature dependent resistive device.

6. The method of claim 5 , wherein:

the temperature dependent resistive device comprises a thermistor; and

the predetermined function comprises the equation:

Temp=[1/(( ln (Index/(16 *Ro ))/Beta)+0.00336)]−273

wherein:

Temp is the Temperature of the Off-Chip Device in Celsius;

Index is a digital value derived from the digitized voltage and the programmable current;

Ro is a resistance of the thermistor in KILOOHMS at 298K Beta is a thermistor value.

7. The method of claim 1 further comprises:

increasing the programmable current when the digital value decreases below a lower threshold value; and

decreasing the programmable current when the digital value increases above an upper threshold value.

8. The method of claim 1 , wherein the devices comprises an off-chip device, and wherein the off-chip device comprises at least one of:

a hard drive and a battery.

9. The method of claim 8 further comprises, when the device is a battery, controlling a battery charge function based on the temperature of the battery.

10. The method of claim 8 further comprises, when the device is a harddrive, controlling the harddrive based on the temperature of the harddrive.

11. The method of claim 1 , that further comprises:

multiplexing the programmable current to a plurality of temperature dependent resistive devices coupled to a plurality of off-chip and/or on-chip devices;

measuring a voltage associated with each of the plurality of temperature dependent resistive devices coupled to the plurality of off-chip and/or on-chip devices;

converting each temperature-dependant voltage to a digital value; and

equating each digital value to the temperature of each of the plurality of off-chip and/or on-chip devices.

12. A digital thermometer to measure a temperature of an off-chip device that comprises:

an on-chip programmable current source to provide a current output;

an analog-to-digital converter operably coupled to sample a temperature-dependant voltage output produced by a temperature dependent resistive device and the current output and convert the temperature-dependent voltage output to a digital value; and

a processing module that receives the digital value and equates the digital value to the temperature of the off-chip device.

13. The digital thermometer of claim 12 , wherein the processing module directs the on-chip programmable current source to:

increase the current output if the digital value decreases below a lower threshold value; and

decrease the current output if the digital value increases above an upper threshold value.

14. The digital thermometer of claim 12 , wherein the analog-to-digital converter comprises a comparator.

15. The digital thermometer of claim 12 , wherein the processing module auto-ranges the on-chip programmable current source so that the current output produces the temperature-dependent voltage output within a predetermined range.

16. The digital thermometer of claim 12 , that further comprises:

a multiplexer that multiplexes the current output to a plurality of temperature dependent resistive devices coupled to a plurality of off-chip and/or on-chip devices; and

a demultiplexer that demultiplexes a plurality of temperature-dependant voltages to the analog-to-digital converter,

wherein the analog-to-digital converter converts each temperature-dependant voltage to a digital value; and

wherein the processing module equates each digital value to the temperature of each of the plurality of off-chip and/or on-chip devices.

17. The digital thermometer of claim 12 , wherein the temperature dependent resistive device comprises a thermistor.

18. The digital thermometer of claim 12 , wherein the processing module equates the digital value to the temperature of the off-chip device with a table relating digital values to temperatures.

19. The digital thermometer of claim 12 , wherein the processing module equates the digital value to the temperature of the off-chip device by calculating the temperature of the off-chip device with a predetermined function wherein the temperature is a function of:

a current supplied by the on-chip current source;

a digitized voltage; and

a set of physical properties that define the temperature dependent resistive device.

20. The digital thermometer of claim 19 , wherein:

the temperature dependent resistive device comprises a thermistor, and

the predetermined function comprises the equation:

Temp=[1/(( In (Index/(16 *Ro ))/Beta)+0.00336)]−273

wherein:

Temp is the Temperature of the Off-Chip Device in Celsius;

Index is a digital value derived from the digitized voltage and the programmable current;

Ro is a resistance of the thermistor in KILOOHMS at 298K; and

Beta is a thermistor value.

21. The digital thermometer of claim 12 , wherein the off-chip device comprises a hard drive.

22. The digital thermometer of claim 12 , wherein the off-chip device comprises a battery.

23. The digital thermometer of claim 12 , wherein the processing module controls a function of the off-chip device based on the temperature of the off-chip device.

24. The digital thermometer of claim 12 , is located on an audio processing chip.

25. An audio processing chip, having a digital thermometer located thereon to measure a temperature of an off-chip device, that comprises:

an on-chip programmable current source to provide a current output;

a temperature dependent resistive device thermally coupled to the off-chip device, that receives the current output to produce a temperature-dependent voltage output;

an analog-to-digital converter to sample the temperature-dependent voltage output and convert the temperature-dependent voltage output to a digital value; and

a processing module that receives the digital value and equates the digital value to the temperature of the off-chip device.

26. The audio processing chip of claim 25 , wherein the processing module directs the on-chip programmable current source to:

increase the current output if the digital value decreases below a lower threshold value; and

decrease the current output if the digital value increases above an upper threshold value.

27. The audio processing chip of claim 25 , wherein the analog-to-digital converter comprises a comparator.

28. The audio processing chip of claim 25 , wherein the processing module auto-ranges the on-chip programmable current source so that the current output produces the temperature-dependent voltage output within a predetermined range.

29. The audio processing chip of claim 25 , that further comprises:

a multiplexer that multiplexes the current output to a plurality of temperature dependent resistive devices coupled to a plurality of off-chip and/or on-chip devices; and

a demultiplexer that demultiplexes a plurality of temperature-dependant voltages to the analog-to-digital converter,

wherein the analog-to-digital converter converts each temperature-dependant voltage to a digital value; and

wherein the processing module equates each digital value to the temperature of each of the plurality of off-chip and/or on-chip devices.

30. The audio processing chip of claim 25 , wherein the temperature dependent resistive device comprises a thermistor.

31. The audio processing chip of claim 25 , wherein the processing module equates the digital value to the temperature of the off-chip device with a table relating digital values to temperatures.

32. The audio processing chip of claim 25 , wherein the processing module equates the digital value to the temperature of the off-chip device by calculating the temperature of the off-chip device with a predetermined function wherein the temperature is a function of:

a current supplied by the on-chip current source;

a digitized voltage; and

a set of physical properties that define the temperature dependent resistive device.

33. The audio processing chip of claim 32 , wherein:

the temperature dependent resistive device comprises a thermistor; and

the predetermined function comprises the equation:

Temp=[1/(( ln (index/(16 *Ro ))/Beta)+0.00336)]273

wherein:

Temp is the Temperature of the Off-Chip Device in Celsius;

Index is a digital value derived from the digitized voltage and the programmable current;

Ro is a resistance of the thermistor in KILOOHMS at 298K; and

Beta is a thermistor value.

34. The audio processing chip of claim 25 , wherein the off-chip device comprises a hard drive.

35. The audio processing chip of claim 25 , wherein the off-chip device comprises a battery.

36. The audio processing chip of claim 25 , wherein the processing module controls a function of the off-chip device based on the temperature of the off-chip device.

Assignments (11)

Continuity (2)