US Patent 10067478 Use of a recirculating delay line with a time-to-digital converter

The resolution of a time to digital converter (TDC) is improved by using a gain stage at the input of the fine TDC. A delay line receives a pulse corresponding to the time information and recirculates the pulse in the delay line by coupling an output of the delay line to an input of the delay line. An integrating fine TDC receives a number of pulses from the delay line corresponding to the desired gain.