chapter  9
58 Pages

- Discriminators

In applications involving radiation sensors, the arrival time of the event is often

unknown. Employing a synchronous discriminator would hence require sampling the

output of the front-end amplifier at a fairly high speed, increasing the power consump-

tion and demanding the routing of high speed digital control lines in close proximity

of very sensitive analog blocks. Even in those applications in which particles arrive

at known times, such as in colliding beam experiments, the simultaneous triggering

of many digital cells can become an issue, especially in chips with many channels.

For these reasons, asynchronous topologies are in general preferred. The picture may

change with ultra-deep submicron technologies (65 nm and beyond), in which the

supply voltage is reduced to 1 V or less and the parasitic capacitance becomes very

small, allowing fast switching at very low power. The discriminator plays a particular

role in those applications requiring the precise tagging of the particle arrival time.

Special techniques have consequently been developed for these high performance

“timing discriminators”.