Experimental demonstration of stochastic comparators for fine resolution ADC without calibration

The paper presents an experimental demonstration of fine-resolution stochastic analog-to-digital converter. The effective LSB resolution and number of comparators versus linear region neighbouring the trip point are introduced by measurement data. The approach is to use a fully differential comparator scheme to suppress input common-mode noise. A layout strategy of manually placing and routing is proposed to reduce systematic variation and to achieve Gaussian random offset distribution. Four testing chips are fabricated in a 180-nm CMOS process and then measured by a low-noise DC measurement setup for fully differential analog inputs. The result shows that a Gaussian offset distribution can be achieved with a reasonable number of comparators. Compared with conventional approach, the effective LSB resolution is 10 times smaller but with less than 10 times of the number of comparators.