A Multispectral Analog Photon-Counting Readout Circuit for X-ray Hybrid Pixel Detectors

In this paper, an all-analog pixel architecture for the readout of X-ray pixel detectors with multiple energy discrimination is proposed. The circuit comprises a self-triggered reset charge amplifier and three distinct channels devoted to the detection on a specific energy band. Each channel is composed of an autocalibrated comparator, an energy window identification logic, and an analog counter with an adjustable dynamic range. A test prototype has been implemented with a standard complementary metal-oxide-semiconductor 0.35-mum technology. The pixel circuitry dissipates 15 muW at 3.3 V, has a noise equivalent charge of 82 e_rms ^- at 200 fF, and allows, on each of the three channels, a dynamic range that exceeds 12 bits. The designed pixel is a square with a 109-mum pitch.