DIET2: A SiPM Readout ASIC for 10 ps TOF-PET application

Positron emission tomography (PET) is currently the most sensitive molecular imaging modality, mainly used for cancer diagnosis and monitoring its response to treatment. The introduction of time-of-flight (TOF) techniques can effectively improve the SNR of images, a CTR of 10 ps is expected to improve the SNR by more than an order of magnitude. 10 ps CTR TOF-PET implementation requires optimization of the entire annihilation photon detection process, including scintillators, photodetectors, readout electronics, etc. Based on the 180 nm process, we designed an 8-channel silicon photomultiplier (SiPM) readout application-specific integrated circuit (ASIC): DIET2 (digitizer with individual energy and timing), which is expected to be applied to the 10 ps TOF-PET system. DIET2 adopts a current-mode structure for signal processing, key circuit including front-end, time to digital converter (TDC), and charge to digital converter (QDC) are integrated in the chip to obtain the time and energy information of the SiPM output signal. For the precision of 10 ps CTR, the main noise sources are optimized. They are noise of frontend, thermal noise of time to amplitude converter (TAC) process, integration nonlinearity (INL) of TDC, and quantization noise of TDC. The simulation results show that the overall timing precision is 8. 65 ps CTR, where the jitter introduced by frontend is 2 ps RMS, the jitter introduced by TAC thermal noise is 1.4 ps RMS, the jitter introduced by TDC INL is 0.6 ps RMS, and the jitter introduced by quantization noise is 0.7 ps RMS. More detailed simulations will be implemented, including power supply noise and the effect of PVT. DIET2 will be fabricated in July and tested around October