28.3 A 5.2Mpixel 88.4dB-DR 12in CMOS X-Ray Detector with 16b Column-Parallel Continuous-Time ΔΣ ADCs

CMOS X-ray detectors used in industrial and medical equipment should provide a full image depth even for a specific region of interest, and require high resolution, low noise, and wide DR in a wafer-scale detector [1], [4]. To achieve a wide DR, a large integration capacitor is required within the pixel to prevent its saturation at high dose, but this degrades image quality at low dose. To facilitate wide DR (>70dB), a conventional detector uses a column-parallel readout with a programmable gain amplifier (PGA) and an ADC [3]. However, the PGA consumes substantially more power and area than the ADC, and its gain control requires multiple X-ray exposures. The use of switched-capacitor (SC) ΔΣ ADC provides wide DR with an improved noise performance [2], [5]. However, its SC input draws high peak current that must be supplied by pixels and reference drivers, and its complex clock distribution also requires high power consumption.