Circuits and methods for current measurements referred to a precision impedance

• US 7,246,016 B2
• Filed: 07/18/2006
• Issued: 07/17/2007
• Est. Priority Date: 11/01/2001
• Status: Expired due to Term

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Roach, Steven D
• Primary Examiner(s): Tsai; Carol S. W.
• Application Number:
  US11/489,378
• Publication Number:
  US 20060259256A1
• Time in Patent Office: 364 Days
• Field of Search: 702/64, 702/57, 702/69, 702/81, 702/189, 323/312
• US Class Current: 702/64
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 19/25 using digital measurement techniques

Abstract

Circuitry and methods for obtaining accurate measurements of current supplied by an integrated circuit are provided. Current calculations are performed using information from a precision termination resistor and from the ratio relationship of two on-chip resistors. The invention provides a way to obtain accurate current measurements without the use of component trimming.

Claims

1. A system comprising:

an integrated circuit;

a first impedance disposed on the integrated circuit;

a second impedance disposed on the integrated circuit;

a first measurement device coupled to the first impedance configured to measure a first voltage drop across the first impedance;

a second measurement device coupled to the second impedance configured to measure a second voltage drop across the second impedance;

a third impedance disposed outside of the integrated circuit;

a third measurement device coupled to the third impedance configured to measure a third voltage drop across the third impedance; and

processing circuitry that utilizes information from the first, second, and third measurement devices to determine a current supplied by the integrated circuit.

2. The circuit of claim 1 wherein the first measurement device is an analog to digital converter.

3. The circuit of claim 1 wherein the second measurement device is an analog to digital converter.

4. The circuit of claim 3 wherein the analog to digital converter further comprises a trimmed voltage reference.

5. The circuit of claim 1 wherein the third measurement device is an analog to digital converter.

6. The circuit of claim 1 wherein the third impedance is a precision resistor.

7. The circuit of claim 1 wherein the third impedance is a switched capacitor circuit.

8. The circuit of claim 1 wherein the third impedance is an external resistor.

9. The circuit of claim 1 further comprising a sinking circuit coupled to the second impedance.

10. A system comprising:

an integrated circuit;

a first resistive element disposed on the integrated circuit;

a second resistive element disposed outside of the integrated circuit;

a first measurement device coupled to the first resistive element configured to measure a first voltage drop across the first resistive element;

a second measurement device coupled to the second resistive element configured to measure a second voltage drop across the second resistive element; and

processing circuitry that utilizes information from the first and second measurement devices to determine a current supplied by the integrated circuit.

11. The circuit of claim 10 wherein the first measurement device is an analog to digital converter.

12. The circuit of claim 10 wherein the second measurement device is an analog to digital converter.

13. The circuit of claim 12 wherein the analog to digital converter further comprises a trimmed voltage reference.

14. The circuit of claim 10 wherein the second resistive element is a precision resistor.

15. The circuit of claim 10 wherein the second resistive element is a switched capacitor circuit.

16. The circuit of claim 10 wherein the second resistive element is an external resistor.

17. The circuit of claim 10 further comprising a sinking circuit coupled to the first resistive element.

18. A system comprising:

an integrated circuit;

a reference voltage source;

a first measurement device configured to measure voltage levels across two impedance elements located on the integrated circuit relative to the reference voltage source;

a second measurement device configured to measure the voltage level across an impedance element external to the integrated circuit relative to the reference voltage source; and

processing circuitry that utilizes information from the first and second measurement devices to determine a current supplied by the integrated circuit.

19. The circuit of claim 18 wherein the first measurement device is an analog to digital converter.

20. The circuit of claim 18 wherein the second measurement device is an analog to digital converter.

21. The circuit of claim 20 wherein the analog to digital converter further comprises a trimmed voltage reference.

22. The circuit of claim 18 wherein the impedance element external to the integrated circuit is a precision resistor.

23. The circuit of claim 18 wherein the impedance element external to the integrated circuit is a switched capacitor circuit.

24. The circuit of claim 18 wherein the impedance element external to the integrated circuit is an external resistor.

25. The circuit of claim 18 further comprising a sinking circuit coupled one of the two impedance elements on the integrated circuit.

26. The circuit of claim 18 wherein the supplied current is a modulation current.

27. A method comprising:

providing an integrated circuit;

providing a first impedance disposed on the integrated circuit;

providing a second impedance disposed on the integrated circuit;

measuring a first voltage drop across the first impedance;

measuring a second voltage drop across the second impedance;

providing a third impedance disposed outside of the integrated circuit;

measuring a third voltage drop across the third impedance; and

utilizing the first, second, and third measurements to calculate a supplied current from the integrated circuit.

28. The method of claim 27 wherein the first measurement provides an analog to digital conversion.

29. The method of claim 27 wherein the second measurement provides an analog to digital conversion.

30. The method of claim 27 wherein the analog to digital conversion further comprises a trimmed voltage reference.

31. The method of claim 27 wherein the third measurement provides an analog to digital conversion.

32. The method of claim 27 wherein the third impedance is a precision resistor.

33. The method of claim 27 wherein the third impedance is a switched capacitor circuit.

34. The method of claim 27 wherein the third impedance is an external resistor.