TDC SAR algorithm with continuous disassembly (SAR-CD) for time-based ADCs

Abstract

This paper introduces a new algorithm and circuit design of Time-to-Digital Converter(TDC) with modified Successive Approximation Register(SAR) algorithm. This design enables continuous pulse disassemble. The input pulse is absolutely compared to pulses of widths proportional to Vfs/2, Vfs/4‥Vfs/N, and each bit is evaluated independent of the previous bit result. Then bits correction is applied after the sample evaluation. A 4bit case study circuit is realized using TSMC CMOS 65nm design technology. The design demonstrated 3.67 Effective Number Of Bits (ENOB) for a sampling frequency of 666 MS\s.