Multi-bit Sigma-Delta TDC Architecture for Digital Signal Timing Measurement

This paper describes the architecture (circuit design) and principles of operation of sigma-delta Sigma-Delta time-to-digital converters (TDC) for high-speed I/O interface circuit test applications, they offer good accuracy with short test times. In particular, we describe multi-bit ΣΔ TDC architectures for fast testing. However, mismatches among delay cells in delay lines degrade the linearity there. Then we propose two methods to improve the overall TDC linearity: a data-weighted averaging algorithm, and a self-calibration method that measures delay values using a ring oscillator circuit. Our MATLAB and Spectre simulation results demonstrate the effectiveness of these approaches.