An application specific integrated circuit for multi anode PMT

The main purpose of this development is to design an "intelligent sensor", composed of one multi anodes PMT, four custom front-end analog chips with embedded analog to digital converter and a pre-processing logical unit. The idea of this design is to improve as most as possible the treatment speed of signals of the PMT. This design must be compact to fit the PMT dimensions, in order to combine them together to form an assembly which will be used in medical imaging research, especially for gamma-ray camera at 144 keV (/sup 99m/Tc) with NaI(Tl) cristal.

I. Introduction

This “intelligent sensor” is designed to fit a 64 anodes PMT. The front-end mixed-signal ASIC contains 16 channels, so 4 chips are necessary to equip the PMT. Each channel consists in an input stage, an integrator, an 8 bits ADC and a shift register. A built-in trigger system allows to start/stop integration and AD conversion. Serial output data are sent to a logical unit (FPGA) which performs a preprocessing, and then, datas are collected on acquisition computer thanks to USB interface (see Fig. 1).