Triroc is a 64-channel silicon photomultiplier (SiPM) readout ASIC targeted for Time-of-Flight Positron Emission Tomograpy (TOF-PET) application. This chip developed for TRIMAGE project which is aimed for building a cost effective tri-modal PET/MR/EEG brain scan.
The low-noise, DC-coupled front-end amplifiers of this ASIC accept both negative and positive input signals thus making it suitable for reading out any SiPM in the market. Moreover, individual input DC level adjustment is available for correcting the non-uniformity of SiPM gain.
In each ASIC channel, the incoming signals will be sent into two different paths: for energy and time measurements. A variable gain semi-gaussien shaper is used for shaping the input signal in energy measurements. The energy conversion is handled by a 10-bit Wilkinson ADC. This ADC is a proven design and it is expected to be linear up to 2500 photoelectrons. Additionally, a charge trigger is available and can be used for events validation at required energy such as 511 keV.
Signal from high speed input pre-amplifier is fed into a discriminator in order to provide a fast trigger for time measurements. A TDC module with coarse and 40 ps fine time is used to time-stamp this trigger.
The digitized data are collected by the digital part which is also capable to validate 511 keV events and reject noise. Running at 80 Mhz, data will be transmitted through 4-bits parallel links. Other features on the digital side are zero suppress readout and TDC data compression. In all, the ASIC should be able to process up to 30k events per second.
Triroc can be operated with minimal external components, since most of the components for SiPM readout are packed internally. This feature makes the ASIC is a good contender in compact multi-channel PET applications. Triroc is designed by using AMS 0.35µm SiGe technology and will be submitted in March 2014.