A 103fsrms 1.32mW 50MS/s 1.25MHz bandwidth two-step flash-ΔΣ time-to-digital converter for ADPLL

A 50-MS/s two-step flash-ΔΣ time-to-digital converter (TDC) using a 2-channel time-interleaved time-domain register with an implicit adder/subtractor demonstrates a 3^rd order noise-shaping. The TDC is fabricated in 40-nm CMOS and consumes 1.2 mA from a 1.1 V supply. At frequencies below 1.25 MHz, the TDC error integrates to 103 fs_rms, which is equal to an equivalent resolution of 1.6 ps.