CDS4C: A novel CDS ASIC for a multi-readout X-ray CCD with a 0.032% INL

This work presents the development of a four-channel correlated double sampling (CDS) ASIC, named CD-S4C, targeting the readout of a type of multi-readout swept charge device (SCD) for applications in the fields of both X-ray spectroscopy and imaging. Compared with conventional CDS architecture based on clamping technique, the innovation of the CDS4C ASIC is that it not only moves the clamping switch out of the signal path but also omits the sampling switch, eliminating the nonlinearity and thermal noise introduced by the these switches. Besides, it is implemented in a fully differential topology which suppresses the second-order harmonic distortion, improving the linearity further more. A theoretical noise analysis taking into consideration of the limited bandwidth of the operational-amplifier (OPA) highly coincides with the simulation results. A prototype of the CDS4C ASIC is fabricated with Global Foundries 0.35μm CMOS process, the preliminary experimental results show that, within the effective input dynamic range of 0~20mV which is equivalent to a wide range of soft X-ray energy band from 0 to 18.25keV, 0.032% integral nonlinearity (INL) and 35.5μV input-referred readout noise are achieved under 200kHz pixel rate with 8× gain, while the total power consumption is only 8.8mW from a single 3.3V supply voltage.