Time-Domain Approach for Analog Circuits: Fine-Resolution TDC and Quick-Start CDR Circuits

As the VLSI process technology scales further and further, analog circuit designs are facing a difficulty in maintaining its dynamic range mainly due to the reduced supply voltage. On the other hand, a time-domain approach, which is a new paradigm of realizing analog functionalities, is becoming superior to the conventional voltage/current-domain circuits thanks to the sharp signal transitions with high-speed transistors. In this paper, first we will briefly discuss the advantage of the time-domain approach in terms of its dynamic range. Then as examples of time-domain circuit designs, a fine-resolution time-to-digital converter based on pulse-shrinking scheme utilizing a built-in offset pulse and a reference-clock-less quick-start clock data recovery circuit based on self-tunable digitally-controlled delay lines will be reviewed.