The improvement of VLSI process technologies over the last twenty years enables us to integrate a large number of transistors on a single chip, and significantly improves the circuit performance. Especially in nano-scale CMOS processes, a time-domain resolution is becoming superior to a voltage-domain resolution due to the high-speed transistors and the reduced supply voltage.
A Time-to-Digital Converter (TDC) quantizes the time-domain analog signal, which is often a time interval between two signal transitions, into a digital signal, and becomes widely used not only for ADPLLs, but also for jitter measurements, timeof- flight range finders, space science instruments, and so on.
In our laboratory, we developed and designed some novel TDCs such as TDC utilizing the TDA which is also developed in our lab., or a TDC utilizing differential pulse-shrinking scheme which realizes robust time resolution. Those TDCs realized ultra-fine time resolution below 1ps.