A 13b 315fsrms 2mW 500MS/s 1MHz bandwidth highly digital time-to-digital converter using switched ring oscillators

Time-to-digital converters (TDCs) were historically used in laser range-finding, automatic test equipment, and timing jitter measurements, but recent developments in the design of high-resolution TDCs have paved the way for mostly digital implementation of PLLs and ADCs. We present a highly digital switched ring oscillator based TDC (SRO-TDC) that achieves noise shaping and is capable of operating at high OSRs. The prototype SRO-TDC achieves an integrated noise of 315fs_rms in a 1 MHz signal band-width at an input carrier and sampling frequencies of 80MHz and 500MHz, respectively while consuming less than 2mW from a 1V supply. It is also capable of operating over a wide range of input carrier frequencies (0.6 to 750MHz) and sampling rates (50 to 750MS/S).