A mixed-signal readout chip for a 7-cell Si-Drift detector in 0.35-μm BiCMOS technology

This paper describes a mixed-signal seven-channel ASIC in 0.35-mum BiCMOS technology for the readout of Si-drift detectors used in X-ray spectroscopy. An integral count rate of more than four million pulses per second can be achieved. Count rate- and photon energy-related changes of the input pulse shape are compensated by a baseline-holding circuit, where the baseline instability remains below 1%. Within an input dynamic range between 1.9 mV and 7.2 mV a non-linearity below 1% can be reached. The equivalent input-noise voltage amounts to 31 muVrms. At maximum output voltage a channel-to-channel crosstalk of ~0.3% was measured. The power consumption of the readout chip is ~15 mW per channel. The functionalities of the main circuit blocks as well as experimental results are presented.