Radiation hardness test of FSSR, a multichannel, mixed signal chip for microstrip detector readout

The Fermilab Silicon Strip Readout (FSSR) chip is a 128-channel, mixed signal circuit, which was designed for processing the signals from the microstrip detectors of the BTeV experiment at the Tevatron collider. The design was carried out in a 0.25 mum CMOS technology, whose intrinsic radiation hardness is supposed to satisfy the application requirements. Such features were further improved by using radiation tolerant layout techniques. A prototype chip, including several variants of the analog front-end electronics and different test structures, has been exposed to 27 MeV protons. A second version of the chip (referred to as FSSR2), where some modifications were implemented with respect to the previous one, has been irradiated with gamma-rays from a ⁶⁰Co source. This paper is devoted to presenting the results of the radiation hardness tests and assessing the suitability of the chip for operation in extremely harsh environments.