PFM2: A 32x32 readout chip for the PixFEL X-ray imager demonstrator

A readout chip, consisting of 32×32 square cells, has been designed in a 65 nm CMOS technology. The circuit will be bump bonded to a slim/active edge pixel sensor to form the first demonstrator for the PixFEL X-ray imager, envisaged for applications to experiments at the next generation X-ray FELs. The pixel pitch is 110 μm, for a total area of about 16 mm2. Different solutions for the readout channel, which includes a charge preamplifier, a time-variant filter and a 10 bit ADC, have been integrated in the chip. In particular, a couple of different versions for the time-variant processor have been implemented. The charge preamplifier is provided with four different gain settings, therefore improving the system capability to comply with photon energies in the 1 keV to 10 keV interval. This work, besides discussing in detail the readout channel and array architecture, will present the first results from the chip characterization.