Patent ID: 8154321

Claim:
A time-differential analog comparator, comprising: a variable frequency signal source coupled to provide a repeating signal having a plurality of periods, wherein each period has a frequency corresponding to a value of an analog input; a counting circuit coupled to count the periods of the repeating signal, wherein the counting circuit is coupled to count in a first direction for a first time interval and coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval; a timing circuit coupled to the counting circuit, wherein the first time interval and the second time interval are determined by the timing circuit, and wherein the timing circuit is further coupled to generate a mode select signal at a time between the first time interval and the second time interval to stimulate a change in the analog input; and an evaluation circuit coupled to the counting circuit and the timing circuit, wherein the evaluation circuit is responsive to a count of the periods of the repeating signal after an end of the second time interval.