An event-driven X-ray CCD imager device uses a floating-gate amplifier or other
non-destructive readout device to non-destructively sense a charge level in a charge
packet associated with a pixel. The output of the floating-gate amplifier is used
to identify each pixel that has a charge level above a predetermined threshold.
If the charge level is above a predetermined threshold the charge in the triggering
charge packet and in the charge packets from neighboring pixels need to be measured
accurately. A charge delay register is included in the event-driven X-ray CCD imager
device to enable recovery of the charge packets from neighboring pixels for accurate
measurement. When a charge packet reaches the end of the charge delay register,
control logic either dumps the charge packet, or steers the charge packet to a
charge FIFO to preserve it if the charge packet is determined to be a packet that
needs accurate measurement. A floating-diffusion amplifier or other low-noise output
stage device, which converts charge level to a voltage level with high precision,
provides final measurement of the charge packets. The voltage level is eventually
digitized by a high linearity ADC.
