A 3-step Low-latency Low-Power Multichannel Time-to-Digital Converter based on Time Residual Amplifier

TL;DR

This paper introduces a three-step low-power, high-resolution multichannel Time-to-Digital Converter (TDC) architecture optimized for integration and high-rate operation, achieving 24.4 ps resolution with minimal power and area.

Contribution

A novel three-step TDC architecture with integrated calibration and low power consumption suitable for multi-channel chips.

Findings

Achieved 24.4 ps resolution in prototype

Power consumption limited to 2.2 mW per channel during operation

Timing precision better than 21 ps RMS

Abstract

This paper proposes and evaluates a novel architecture for a low-power Time-to-Digital Converter with high resolution, optimized for both integration in multichannel chips and high rate operation (40 Mconversion/s/channel). This converter is based on a three-step architecture. The first step uses a counter whereas the following ones are based on two kinds of Delay Line structures. A programmable time amplifier is used between the second and third steps to reach the final resolution of 24.4 ps in the standard mode of operation. The system makes use of common continuously stabilized master blocks that control trimmable slave blocks, in each channel, against the effects of global PVT variations. Thanks to this structure, the power consumption of a channel is considerably reduced when it does not process a hit, and limited to 2.2 mW when it processes a hit. In the 130 nm CMOS technology used for the prototype, the area of a TDC channel is only 0.051 mm2. This compactness combined with low power consumption is a key advantage for integration in multi-channel front-end chips. The performance of this new structure has been evaluated on prototype chips. Measurements show excellent timing performance over a wide range of operating temperatures (-40{\deg}C to 60{\deg}C) in agreement with our expectations. For example, the measured timing integral nonlinearity is better than 1 LSB (25 ps) and the overall timing precision is better than 21 ps RMS.