Development of an 8-channel time based readout ASIC for PET applications

An eight-channel readout ASIC has been developed for reading out signals from Silicon Photomultiplier (SiPM) for PET applications. It converts both signal charge and occurring time to digital timing pulses and only needs TDC. It has the advantages of simplified circuit design, reduced power consumption and suitable for large number of readout channels. The ASIC uses a fully current mode preamplifier to obtain high bandwidth (>;100MHz) with a few mW/ch power consumption. The dynamic range for charge measurement is adjustable and can be extended up to 10³ pC. The chip has been fabricated in 0.35μm 2P4M CMOS technology. A test prototype board for ASIC evaluation has been developed and the preliminary tests show the time jitter is 150ps (rms) by electronics only with injected 30 ns rise time signals, and the coincidence timing is about 1.7 ns (FWHM) for 511 keV photo peak events with LYSO/SiPM detectors. The charge dynamic range is measured to be ~10bit for electronics only, and better than 1% for detector signals. A simple theoretic analysis shows that the timing and charge resolutions are limited dominately by the detector dark noise in our test and will be studied further. Preliminary evaluations show that the ASIC´s functionalities and performance targets have been successfully achieved.