Patent ID: 8193822

Claim:
A circuit for determining a value of a capacitor, comprising: first circuitry for generating a first indication when a variable voltage across the capacitor crosses a threshold voltage; second circuitry for generating a second indication when a reference voltage across a reference capacitor crosses the threshold voltage; control logic responsive to the first and second indications for generating a control signal indicating whether at least one of the first or second indications occurs before the other of the first or second indications; a successive approximation engine for generating an N-bit control value responsive to the control signal; a variable current source responsive to the N-bit control value for generating a variable current to the first circuitry; a reference current source for generating a reference current to the second circuitry; and wherein the value of the capacitor is determined by associated processing circuitry responsive to a value of the reference capacitor, the reference current and the variable current provided by the variable current source when the variable voltage substantially equals the reference voltage.