A clockless time-to-digital converter

Existing implementations of time-to-digital converters are based on the use of reference clocks. In the paper, a new method of clockless time-to-digital conversion (TDC) is proposed where the discretized time interval is first converted to the corresponding charge packet, and next processed in the charge domain by successive charge redistribution. The proposed circuit configuration is extremely simple and contains only binary-weighted capacitor array, current source, group of controlled switches, 2 comparators and asynchronous state machine. The TDC is self-timed and does not contain the DAC.