PACIFIC: SiPM readout ASIC for LHCb upgrade

Highlights: • A new mix-signal silicon photomultiplier readout ASIC is presented. • Direct anode connection with voltage and impedance control at this node. • Fast shaping and integration with configurable 2-bit non-linear output. • It has demonstrated single photoelectron detection capability. A new 64-channel mixed-signal ASIC is presented: PACIFIC. It was developed in TSMC 130 nm CMOS technology for the readout of the Scintillating Fibre Tracker, as a part of the LHCb upgrade. This detector is based on 250 $\mu$ m scintillating fibers readout by custom designed 128-channel silicon photomultiplier arrays. It will cover a total area of 340 m², distributed over the 12 planes that compose it. The sensors are connected directly to PACIFIC without any interface components. The ASIC acquires the current pulses using a current conveyor. A fast double pole-zero cancellation shaper is used to minimize spillover. The charge is then collected using gated integrators, with a twofold interleaved scheme to minimize dead time. The resulting voltage level is digitized with a configurable 2 bit non-linear flash ADC. The output is a 320 Mbps differential signal produced by the serializers, which gather the results from four adjacent channels.