Circuitry and methods for current measurements referred to a precision impedance
View Patent ↗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.
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.