Patent ID: 7355387
Filing Date: 2008-04-08
Classification: G01R

Abstract:
1. A system for measuring the delay time between first and second signals, comprising: a first delay line having an input coupled to receive the first signal in a measurement mode and to receive a periodic signal in a calibration mode, the first delay line being operable to generate from the first signal or the periodic signal a delayed signal with a delay corresponding to a delay value; a first comparator operable in the measurement mode to compare the timing of the delayed signal with the timing of the second signal and to generate a first match signal when transitions of the delayed signal substantially coincide with transitions of the second signal, the delay value being used by the first delay line when the first match signal is generated being used by the first delay line in the calibration mode; a phase interpolator coupled to receive the periodic signal, the phase interpolator being operable to phase offset the periodic signal by a magnitude corresponding to a phase value to generate a phase-offset signal; a second comparator operable in the calibration mode to compare the timing of the delayed signal with the timing of the phase-offset signal and to generate a second match signal when transitions of the delayed signal substantially coincide with transitions of the phase offset signal; and a control unit coupled to the delay line, the phase interpolator and the first and second comparators, the control unit being operable to apply the delay value to the first delay line that was being applied to the first delay line when the first match signal was generated, the control unit further being operable to apply a series of phase values to the phase interpolator that causes the phase interpolator to phase offset the periodic signal over a range of phases until the second match signal is generated, the phase value being applied to the phase interpolator when the second match signal is generated providing an indication of the delay between the first and second signals.