A synchronous analog very front-end in 65 nm CMOS with local fast ToT encoding for pixel detectors at HL-LHC

This work describes the design, in 65 nm CMOS, of a very compact, low power, low threshold synchronous analog front-end for pixel detectors at HL-LHC. Threshold trimming is avoided using offset compensation techniques. Fast ToT encoding is possible, as the comparator can be turned into a Local Oscillator up to several hundreds MHz. Two small prototypes have been submitted and tested; a X-ray irradiation up to 600 Mrad has been performed. Detailed results in terms of gain, noise, ToT and threshold dispersion are presented. This design will be part of the CHIPIX65 demonstrator and of the RD53A chip.