SENSROC12: A Four-Channel Binary-Output Front-End Readout ASIC for Si-PIN-Based Personal Dosimeters

A commercial silicon p-i-n (Si-PIN) photodetector is proposed for electronic personal dosimeters (EPDs) for the sake of the detection of low-energy X-rays and/or γ-rays. Since the EPD is a portable device supplied with a battery, front-end electronics with small size and low power dissipation are required. This paper presents a fully-customized low-power front-end readout application-specific integrated circuit (ASIC) as a solution for this application. The ASIC includes four-channel analog front-ends with a digital interface. Each channel mainly includes a charge sensitive amplifier (CSA), a CR-RC
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pulse shaper, an output buffer, a discriminator, and a digital-to-analog converter (DAC). An I
²
C interface and shift registers are designed to control the analog blocks. The modeling of equivalent noise charge (ENC) is discussed to optimize the circuit design. A prototype ASIC is designed in 0.35-μm CMOS mixed-signal 3.3 V process. The die size is 2.4 mm × 2.4 mm. The preliminary test results are obtained. The input charge is 0.2-15 fC. The ENC is 119 e-+ 15.9 e-/pF under the power dissipation of about 1.25 mW/channel. The proposed ASIC can well meet the requirements of the EPD and other radiation detector systems.