Circuitry and methods for current measurements referred to a precision impedance

• US 7,103,487 B2
• Filed: 07/06/2005
• Issued: 09/05/2006
• 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:
  US11/176,553
• Publication Number:
  US 20050261846A1
• Time in Patent Office: 426 Days
• Field of Search: None
• 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 circuit that determines a current supplied by an integrated circuit comprising:

a sensing impedance disposed on the integrated circuit;

a modulation impedance;

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

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

a termination impedance;

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

processing circuitry configured to receive information from the first, second, and third measurement devices and calculate supplied current therefrom.

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 1 wherein the third measurement device is an analog to digital converter.

5. The circuit of claim 1 wherein the second analog to digital converter further comprises a trimmed voltage reference.

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

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

8. The circuit of claim 6 wherein the termination impedance is an external resistor.

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

10. The circuit of claim 1 wherein the supplied current is a modulation current.