Time-to-Digital Converter Basics

Abstract

On the basis of a generic mixed-signal system the scaling difficulties of analog and mixed-signal circuits based on a signal representation in the voltage domain are discussed for nanometer CMOS technologies. Therewith, the advantages of a signal representation in the time domain are emphasized. The primary approach to time-to-digital converters (analog TDCs) based on a two step approach translating the time interval into a voltage and this voltage into a digital value is explained. Analog impairments and resolution limitations are examined. Counter based time interval measurement and delay-line based TDCs (digital TDCs) are introduced and analyzed with respect to operating principle, basic implementation issues, and quantization error, i.e. resolution.