A 12 bit 40 MSPS SAR ADC with a redundancy algorithm and digital calibration for the ATLAS LAr calorimeter readout

We present a SAR ADC with a generalized redundant search algorithm offering the flexibility to relax the requirements on the DAC settling time. The redundancy also allows a digital background calibration, based on a code density analysis, to compensate the capacitor mismatch effects. The total number of capacitors used in this architecture is limited to a half of the one in a classical SAR design. Only 2 unit capacitors were necessary to reach 12 bit resolution, and the switching algorithm is intrinsically monotonic. The design is fully differential featuring 12 bit 40 MS/s in a CMOS 130 nm 1P8M process.