FPGA-based flexible CCD control system for X-ray astronomy payloads

We have developed a Field Programmable Gate Array (FPGA)-based Charge Coupled Device (CCD) data acquisition system, which will be used in the focal plane of Soft X-ray Telescope (SXT) on India's first multi-wavelength astronomy satellite—ASTROSAT. The use of FPGA allows a flexible system that can be used for driving almost all types of CCDs with very little modifications. It can generate clocks up to 1 MHz with adjustable phase. CCD biases and clock amplitudes can be generated and uploaded very easily. Electronic noise is reduced by reading the CCD when FPGA is at its minimum activity. CCD22, a MOS CCD developed in Europe, was biased and clocked by using this system. Each pixel is read at 6 μs intervals. The energy resolution of 55Fe at Kα peak has a full-width at half-maximum of ≈153 eV and the readout noise of our system is ≈8e— rms.