Speaker
Description
A readout channel for applications to X-ray diffraction imaging at free electron lasers has been developed in a 65 nm CMOS technology. The analog front-end circuit can achieve an input dynamic range of 100 dB by leveraging a novel signal compression technique based on the non-linear features of MOS capacitors. Trapezoidal shaping is accomplished through a transconductor and a switched capacitor circuit, performing gated integration and correlated double sampling. A small area, low power 10 bit successive approximation register (SAR) ADC, operated in a time-interleaved fashion, is used for numerical conversion of the amplitude measurement. A prototype chip has already been fabricated and characterized. A new readout chip, consisting of 32x32 square cells, has been designed to be bump bonded to a slim/active edge pixel sensor and form the first demonstrator for the PixFEL X-ray imager. The pixel pitch is 110 μm, for a total area of about 16 mm$^2$. In particular, a couple of different versions for the time variant processor have been implemented and, as compared to the prototype version, the charge preamplifier is provided with a larger range of 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 results from the chip characterization.
