16bit multi-energy level detecting photon counting ROIC

This paper summarizes progress of development of LXT-RPOIA, a 64 × 64 pixel 16bit multi-energy level detecting photon counting Readout IC (ROIC) for hybrid type X-ray imaging devices, with a programmable gain adjustment mechanism. The chip core is comprised of a matrix arrayed single pixels, which are capable of detecting and discriminating incoming photoelectric signals of up to four different energy levels based on four reference voltages. Digital control blocks and a column addressing block are embedded within the IC for generating various necessary control signals, and data reading out. A single pixel is equipped with a Charge Sensitive Amplifier (CSA) and a Variable Gain Amplifier (VGA), and four individual discriminators as well as four counters made of 16bit Linear Feedback Shift Register (LFSR). The CSA and VGA can each operate at three different gain modes: high gain; typical gain; low gain. Degree of amplification is determined by the ratio of embedded passive feedback components such as capacitors and resisters which are controlled by switches in accordance with an external digital control signal. Data processing is done in digital, for discrete data reading out. The data acquired from a pixel counter is relayed to a next corresponding counter, pixel-to-pixel basis. The data come out from four channels of 1 bit serial data lines, which account for four different energy levels' discrimination. The LXT-RPOIA is a prototype chip, designed and manufactured in a 6-metal O.18J.lm CMOS technology. The chip is currently being tested, and an updated version will be ready in near future.