ERICA: an energy resolving photon counting readout ASIC for X-ray in-line cameras

We present ERICA (Energy Resolving Inline X-ray Camera) a photon-counting readout ASIC, with 6 energy bins. The ASIC is composed of a matrix of 8 x 20 pixels controlled by a global digital controller and biased with 7 independent digital to analog converters (DACs) and a band-gap current reference. The pixel analog front-end includes a charge sensitive amplifier with 16 mV/ke(-) gain and dynamic range of 45 ke(-). ERICA has programmable pulse width, an adjustable constant current feedback resistor, a linear test pulse generator, and six discriminators with 6-bit local threshold adjustment. The pixel digital back-end includes the digital controller, 8 counters of 8-bit depth, half-full buffer flag for any of the 8 counters, a 74-bit shadow/shift register, a 74-bit configuration latch, and charge sharing compensation processing to perform the energy classification and counting operations of every detected photon in 1 mu s. The pixel size is 330 mu m x 330 mu m and its average consumption is 150 mu W. Implemented in TSMC 0.25 mu m CMOS process, the ASIC pixel's equivalent noise charge (ENC) is 90 e(-)RMS connected to a 1mm thickness matching CdTe detector biased at -300V with a total leakage current of 20 nA.