A new four-side abuttable ASIC for high-resolution multi-energy CT imaging detector arrays

We have developed a new readout ASIC for multienergy CT applications, which can be flip-chip bonded directly to a two-dimensional solid-state pixel detector. Its initial intended use is in CT breast imaging. This chip has an array of 80 × 96 readout channels with a pitch of 0.2 mm × 0.2 mm. The design uses through-silicon vias for the ASIC´s power, bias and digital 1/0 connections to allow for a fully abuttable layout with a die size of 19.1 mm × 16.3 mm. Each channel has a charge-sensitive amplifier with individually adjustable parameters such as gain and baseline offset. The amplifiers are designed for count rates up to 1.25 × 10⁸ photons per second per square millimeter (5 × 10⁶ photons per second per pixel). The amplifier signals are discriminated by four comparators and counted in 12-bit pulse counters. The readout dead time is kept at negligible levels by copying each counter´s data to its own dedicated readout register at the end of each count period, for readout during the following period. Reading the more than 30,000 registers can be accomplished in less than 0.5 ms, allowing for a frame rate of 2000 frames per second.