Time-to-digital converter using time stamp extrapolation

Abstract

A time-to-digital converter starts a ramp signal generator when a trigger signal is received. The ramp signal generator outputs a signal with a substantially constant slope. The output of the ramp signal generator is sampled at two or more reference points. The sampled amplitudes and times at which the samples are taken are stored. An extrapolater calculates the time at which the ramp signal started from the stored amplitudes and times of the samples. Alternatively, the output of the ramp signal generator may be sampled at a periodic rate in which case only the sampled amplitudes and the time of the first sample are stored. In this manner, the time of the trigger signal can be accurately detected without the need for multiple reference signals.