Integrated, CMOS, constant-fraction timing discriminator for multichannel detector systems

An integrated, CMOS, constant-fraction timing discriminator (CFD) that is designed to accommodate the special requirements of large, multichannel detector systems is described. This CFD features on-chip, zero-crossing shaping and an automatic walk setting to limit the number of user adjustments. The circuit is realized in the Orbit 1.2 micron, N-well, CMOS process and operates with a 5V power supply. The time walk in a 100:1 dynamic range (-15mV to -1.5V) is less than ±250ps for a 10ns rise time - 10ns fall time signal, yet the power dissipation is about 2mW/channel. The discriminator has a 170μM pitch, is 800μM long, and is structured for arraying multiple channels on a single die.