A Flexible 18-Channel Multi-Hit Time-to-Digital Converter for Trigger-Based Data Acquisition Systems

This paper presents the design of a low power, compact multi-channel single-shot time-to-digital converter (TDC) capable of handling multiple hits per channel. The system has 17 hit channels and 1 trigger channel and is designed to meet the requirements of the iron calorimeter detector in the India-based neutrino observatory. The TDC core consists of a delay chain stabilized by a delay-locked loop (DLL) and synchronous counters. The digital backend is programmable to allow for multiple configurations during the operation. The common core to all channels with concurrent accessibility, choice of core clock frequency optimizing the trade-offs between performance, power and area, and optimal backend logic result in a compact and low power design. It achieves a single-shot precision better than 65 ps. The $0.13\,\mathrm {\mu m}$ chip occupies an active area of 3.72mm2 and consumes 3.4mW per channel. This paper also reviews the theory on how timing precision is defined for a single-shot TDC and explains how the test plan can be devised based on the jitter in the system.