LYRA: A Multi-Chip ASIC Designed for HERMES X and Gamma Ray Detector

We present an Application Specific Integrated Circuit (ASIC), called LYRA, specifically designed for the HERMES project (High-Energy Rapid Modular Ensemble of Satellites). The goal of the HERMES project is to implement a constellation of nano-satellites able to detect and localize the Gamma Ray Bursts (GRBs) coming from the deep space. Due to the high-energy events, a "double detection" mechanism has been adopted: Gadolinium Aluminum Gallium Garnet (GAGG) scintillators (for high-energy photons) are coupled to Silicon Drift Detectors (SDD) used also for direct detection of low energy photons. Since the detection unit is composed of 120 SDDs and long connections between ASIC and detector must be avoided, the readout electronics has been organized in a multi-chip architecture: 30 LYRA Front-End (FE-LYRA) chips placed close to the anode of the SDDs send their pre-processed signals, in current mode, to a 32-channel LYRA Back-End chip (BE-LYRA). LYRA ASIC has an input dynamic range of 5.2 fC that allows to process signal from photons up to 2.2 MeV with a linearity error between +/- 1.5%. The intrinsic Equivalent Noise Charge is 18 el. r.m.s. at 1.6 mu s peaking time and the power consumption is 520 mu W per channel.