Updates on the Multi-channel LYRA ASIC for X/ \(\gamma \) - Ray Spectrometer Onboard HERMES Space Mission

The upgraded version of the front-end electronics of the X-/ \(\gamma \) -ray detection instrument of the HERMES mission, whose goal is to observe and localize Gamma Ray Bursts (GRBs), through a constellation of nano-satellites, is presented. Since the detection unit is composed of 120 Silicon Drift Detectors (SDDs), coupled to 60 Cesium-doped Gadolinium-Aluminum Gallium Garnet (Ce: GAGG) scintillators and long connections between the preamplifier and detector must be avoided, the readout ASIC, named LYRA, has been organized in a multi-chip architecture: 120 Front-End (LYRA-FE) chips placed close to the anode of the SDDs send their pre-processed signals, in current mode, to four 32-channel Back-End chip (LYRA-BE). LYRA ASIC has a maximum input charge specification of 5.2 fC (2.2 MeV in GAGG) with a linearity error between ±1.5%. An upgraded version of the LYRA-BE ASIC has been designed to improve uniformity due to process, voltage and temperature (PVT) variations between channels in terms of parameters and performance. The simulated intrinsic Equivalent Noise Charge is 14 electrons rms at 1.6  \(\upmu \) s peaking time with a nominal power consumption of 600  \(\upmu \) W/channel. From Monte Carlo simulations, significant improvements are visible in the dispersion of parameters between channels. The dispersion of the channel trigger delay was reduced from 42.5% to 11% (±165 ns), from 26% to 11% in the conversion gain.