FSSR2, a self-triggered low noise readout chip for silicon strip detectors

The FSSR2 is the second release of the Fermilab Silicon Strip Readout Chip. The chip has been designed and fabricated in a 0.25 µm CMOS technology for high radiation tolerance. The first release, simply called the FSSR, was a prototype version with many different analog front-end configurations. The best solution was chosen for the FSSR2 chip to optimize the noise, according to criteria discussed in this paper. The FSSR2 has been designed for the silicon strip detectors of the BTeV experiment. The chip services 128 strips and provides address, time and magnitude information for all hits. Several programmable features are included in FSSR2, such as an internal pulser, a baseline restorer and a signal peaking time selectable among four values in the range between 65 ns and 125 ns. The circuit design and the performance of FSSR2 are discussed in this paper.