A time-of-flight system on a chip suitable for space instrumentation

A time-of-flight (TOF) system-on-a-chip (SoC) for precise time interval measurement at low power and high rate has been developed. A micro-channel plate (MCP) electron multiplier typically produces the start and stop of a radiation event to be processed. The TOF chip includes two Constant Fraction Discriminators (CFDs) and a Time to Digital Converter (TDC). The CFDs interface to start and stop anodes through two simple preamplifiers and perform the signal conditioning for time walk compensation. The TDC portion digitizes the time difference with reference to an external precise oscillator. A first version of the TOF chip developed in a 0.8 u CMOS process achieved ∼350 ps total time resolution, including time walk and time jitter, with ∼20 mW power consumption at a rate of ∼100 K events/sec and ∼30 mW @ 1Mevents/sec. This chip is part of the HENA instrument of the NASA/IMAGE mission launched in March 2000 and is baselined for many other missions including the Energetic Particle Sensor (EPS) of Messenger etc.