A low-power 2-D ASIC for high-resolution gamma-ray spectroscopy

We have developed a new readout ASIC for high-resolution gamma-ray spectroscopy, which can be flip-chip bonded directly to a two-dimensional solid-state pixel array. This chip, called DANA-3 (Detector Array for Nuclear Applications), has a 16 × x16 array of anode readout channels with a pitch of 0.5 mm × 0.5 mm, plus an extra channel optimized for the cathode signals. To minimize power consumption, the ASIC was designed in a 0.18 μm process. To further reduce power dissipation, we incorporated automatic switching between different modes of operation (Watchdog, Counting, and Spectroscopy) depending on user-selectable radiation level thresholds, an ability to power down unused channels, and a low-power, low-noise differential I/O interface. Power dissipation ranges from 7 mW in watchdog mode to 50 mW with all channels enabled in spectroscopy mode. In the latter mode, the circuit features low-noise, high-energy resolution performance and allows for depth-of-interaction optimization using the cathode signal. The ASIC layout is three-side abuttable, so individual circuits can be combined into larger arrays. For optimal performance of the ASIC in different applications the main parameters of the analog channels can be programmed (globally or individually) over a wide range. In this paper we describe the ASIC design details and preliminary results of lab testing and characterization, including noise measurements and testing with pulser signals.