A two-stage pipelined cyclic ADC for X/Gamma spectroscopy

Abstract

The paper presents a cyclic analog to digital converter (ADC) used for gamma spectroscopy. The 10-bit ADC has an input signal range /spl plusmn/0.8V with the resolution near 1mV. The cyclic architecture greatly simplifies the design of comparators in conventional successive approximation ADCs for such a high-resolution requirement. To reach a sampling rate above 1MHZ, we applied a two-stage pipeline technique. Simulation tests indicate that the design can achieve a signal to noise ratio about 56dB with the maximum DNL about 0.8LSB. The unit-gain bandwidth of operational amplifiers and the mismatching of passive components mainly limit the accuracy and the differential non-linearity (DNL) of the proposed ADC. We applied the sliding scale technique with a 6-bit slider to reduce such effects and to improve DNL further down to about 2%. The design is implemented using modern 0.35um 2P4M CMOS integrated circuit technology. The overall circuit power consumption is less than 100 mW with a 3V power supply, which is well suited for portable measurement and remote sensing applications.