A Fast Front-End Readout Design for NICA-MPD Shashlik Electromagnetic Calorimeter

Silicon photomultipliers (SiPMs) are highly valued for their excellent light response and high-gain characteristics, yet their application in fast timing scenarios is often limited by their high terminal capacitance, typically over 300 pF. In electromagnetic calorimeters (ECALs), sub-nanosecond time measurements allow these detectors to function as supplementary time-of-flight (TOF) devices, specifically aiming for a time resolution of 150 ps in the Nuclotron-Based Ion Collider Fañility (NICA)-multipurpose detector (MPD). To address these challenges, this study proposes a novel front-end readout electronics design featuring a two-stage common-base trans-impedance preamplifier and a 12-bit 200-MS/s pipelined successive-approximation-register (SAR) analog-to-digital converter (ADC). Extensive SPICE simulations, using the Hamamatsu S13360-6025 as the input source, demonstrate the preamplifier’s rapid rise time and good linearity. The experimental results from laser testing confirm that this fast preamplifier design achieves a remarkable time resolution of better than 20 ps. The ADC circuit, designed using the TSMC65nmLP process, employs a two-stage pipelined SAR structure with a two-step conversion technique (6 bit +7 bit), incorporating redundancy in the second step. Testing at a 160-MHz sampling rate with an 80-MHz input condition showed that, at Vpk <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ = -1$ </tex-math></inline-formula> dBFS, the ADC’s fast Fourier transform (FFT) spectrum analysis yielded an effective number of bits (ENOBs) of 9.34 and a spurious-free dynamic range (SFDR) of 73.8 dBc. Preliminary system-level timing assessments under a 200-MHz sampling rate revealed that waveforms with three-four sampling points on the rising edge, with a rise time of 15–20 ns, achieved a time resolution of approximately 20 ps.