Determining a temperature coefficient value of a resistor

1. Circuitry for determining a temperature coefficient value of a resistor, the circuitry comprising:

circuitry for supplying an AC current signal to the resistor;

circuitry for measuring a first voltage across the resistor when the AC current signal is supplied; and

processing circuitry configured to determine the temperature coefficient value based on a thermal resistance value of a junction surrounding the resistor and a harmonic distortion value of the first voltage.

2. Circuitry according to claim 1 , wherein the resistor is an integrated resistor of an integrated circuit.

3. Circuitry according to claim 1 , wherein the harmonic distortion value is a third harmonic distortion value or a second harmonic distortion value.

4. Circuitry according to claim 1 , wherein the thermal resistance value is a predefined value based on material properties of the junction.

5. Circuitry according to claim 1 , wherein the circuitry further comprises:

circuitry for supplying a DC current signal to a resistive element for a predefined period of time to dissipate power in the resistive element; and

circuitry for measuring a second voltage across the resistive element when the DC current signal is supplied,

wherein the processing circuitry is further configured to estimate a power dissipated by the resistive element in the predetermined period of time based on the second voltage.

6. Circuitry according to claim 5 , wherein the processing circuitry is further configured to estimate the power dissipated by the resistive element in the predetermined period of time based on the second voltage and a resistance value of the resistive element.

7. Circuitry according to claim 5 , wherein the processing circuitry is further configured to estimate a thermal resistance value of a junction surrounding the resistor based on the estimated power dissipated and a measured change in a temperature in the vicinity of the resistor over the predefined period of time.

8. Circuitry according to claim 7 , wherein the processing circuitry is configured to determine the temperature coefficient value based on the estimated thermal resistance value and the first voltage.

9. Circuitry according to claim 7 , wherein the circuitry comprises temperature sensing circuitry configured to output one or more signals indicative of the measured change of temperature to the processing circuitry.

10. Circuitry according to claim 9 , wherein the temperature sensing circuitry comprises one or more of:

a resistor having a known temperature coefficient;

a diode; and

a transistor.

11. Circuitry according to claim 5 , wherein the resistive element comprises the resistor.

12. Circuitry according to claim 5 , wherein the DC current signal comprises a signal of a constant amplitude.

13. Circuitry according to claim 1 , wherein the AC current signal comprises a sinusoidal current signal.

14. Circuitry according to claim 1 , wherein a temperature to resistance transfer function of the resistor comprises a polynomial function comprising a plurality of different temperature coefficients, each associated with a polynomial term of the polynomial function.

15. An integrated circuit comprising circuitry according to claim 1 .

16. An integrated circuit according to claim 15 , further comprising an integrated current sense resistor.

17. An integrated circuit according to claim 16 , further comprising an integrated current sense resistor.

18. An electronic device comprising an integrated circuit according to claim 17 .

19. An electronic device according to claim 18 , wherein the electronic device comprises a mobile telephone, a tablet or laptop computer, a wearable device, a gaming device, a virtual reality or augmented reality device.

20. Circuitry for determining a thermal resistance value of a junction surrounding a resistor, the circuitry comprising:

circuitry for supplying a DC current signal to a resistive element for a predefined period of time to dissipate power in the resistive element; and

circuitry for measuring a voltage across the resistive element when the DC current signal is supplied,

wherein the processing circuitry is further configured to:

estimate a power dissipated by the resistive element in the predetermined period of time based on the measured voltage and a resistance value of the resistive element; and

estimate a thermal resistance value of the junction surrounding the resistor based on the estimated power dissipated and a measured change in a temperature in the vicinity of the resistive element over the predefined period of time.

21. Circuitry according to claim 20 , wherein the resistive element comprises the resistor.

22. Circuitry according to claim 20 , wherein the DC current signal comprises a signal of a constant amplitude.

23. Circuitry according to claim 20 , wherein the resistor is an integrated resistor of an integrated circuit.

24. An integrated circuit comprising circuitry according to claim 20 .

25. A method for determining a temperature coefficient value of a resistor, the method comprising:

supplying an AC current signal to the resistor;

measuring a first voltage across the resistor when the AC current signal is supplied; and

determining the temperature coefficient value based on a thermal resistance value of a junction surrounding the resistor and a harmonic distortion value of the first voltage.

26. A method according to claim 25 , wherein the method further comprises:

determining a temperature associated with the resistor; and

estimating a resistance value of the resistor at the determined temperature based on a reference resistance value of the resistor, the determined temperature, and the temperature coefficient value.

27. A method according to claim 26 , wherein the resistor is a current sense resistor of current sense circuitry, wherein the method further comprises dynamically calibrating the current sense circuitry based on the estimated resistance value at the determined temperature.

28. A method according to claim 26 , further comprising estimating a current through the resistor based on the estimated resistance value at the determined temperature.

29. A method for determining a thermal resistance value of a junction surrounding a resistor, the method comprising:

supplying a DC current signal to a resistive element for a predefined period of time to dissipate power in the resistive element;

measuring a voltage across the resistive element when the DC current signal is supplied;

estimating a power dissipated by the resistive element in the predetermined period of time based on the measured voltage and a resistance value of the resistive element; and

estimating a thermal resistance value of the junction surrounding the resistor based on the estimated power dissipated and a measured change in a temperature in the vicinity of the resistive element over the predefined period of time.