Qualification of a high-resolution on-chip injection circuit for the calibration of the DSSC X-ray imager for the European XFEL

The availability of on-chip sources with high degree of accuracy able to probe the response of the x-ray imaging detectors in all the conditions foreseen at the European XFEL is a key issue in order to implement automated procedures in order to trim gain and offset of each individual pixel channel to the desired target gain mode with the required degree of accuracy at the XFEL beamline/experiment. In the F2 readout ASIC of the DSSC instrument (DEPFET Sensor with Signal Compression) an improved 13 bit voltage DAC coupled to an electrical injection circuit has been implemented. A thorough measurement campaign to qualify the F2 DAC and the injected charge was conducted on a 64x64 miniSDD-F2 chip as a function of all relevant parameters.