Patent ID: 7187310

Claim:
A method of background calibrating a circuit to be calibrated having a plurality of circuit elements and providing an output residue having a dynamic range for measurement, the method comprising: switching one of said circuit elements to be substituted by an equivalent circuit element within said circuit; injecting at least one calibration signal into at least one of said circuit elements, wherein said calibration signal causes a measurable change in said output residue; measuring said change; calculating a calibration parameter for said circuit based on said change; and performing a calibration correction to an output of said circuit using said parameter, wherein said injecting comprises: providing at least two calibration signals to operate in said circuit in a subtractive manner so that said output residue remains within said dynamic range; providing a group of different imprecise voltages for said calibration signals having at least one value that used alone would cause said residue to lie outside said dynamic range and at least one value that used alone would cause said residue to lie within said dynamic range; selecting a series of different combinations of ones of said group of imprecise voltages for injection in said subtractive manner, said series of combinations including one of said imprecise voltages to be isolated once, a remainder of said imprecise voltages each used in two of said different combinations, with one of said different combinations comprising a zero voltage and one of said imprecise voltages having a value that used alone would cause said residue to lie within said dynamic range; and injecting in said circuit each of said different combinations of said imprecise voltages as said calibration signals; said measuring comprising measuring said change for each of said different combinations, and said calculating said calibration parameter comprises calculating, from a sum of said change measured for each of said different combinations, a value as a function of said one of said imprecise voltages to be isolated independently of said remainder of said imprecise voltages.