Abstract

This thesis describes the development of a high precision time-to-digital converter (TDC) in which the conversion is based on a counter and three-stage stabilised delay line interpolation developed in this work.

The biggest design challenges in the design of a TDC are related to the fact that the arrival moment of the hit signals (start and stop) is unknown and asynchronous with respect to the reference clock edges. Yet, the time interval measurement system must provide an immediate and unambiguous measurement result over the full dynamic range. It must be made sure that the readings from the counter and the interpolators are always consistent with very high probability. Therefore, the operation of the counter is controlled with a synchronising logic that is in turn controlled with the interpolation result. Another synchronising logic makes it possible to synchronise the timing signals with multiphase time-interleaved clock signals as if the synchronising was done with a GHz-level clock, and enables multi-stage interpolation. Multi-stage interpolation reduces the number of delay cells and registers needed.

The delay line interpolators are stabilised with nested delay-locked loops, which leads to good stability and makes it possible to improve single-shot precision with a single look-up table containing the integral nonlinearities of the interpolators measured at the room temperature.

A multi-channel prototype TDC was fabricated in a 0.6 μm digital CMOS process. The prototype reaches state-of-the-art rms single-shot precision of better than 20 ps and low power consumption of 50 mW as an integrated TDC.