PACES: A Partition-Centering-Based Symmetry Placement for Binary-Weighted Unit Capacitor Arrays

Abstract

Capacitor matching influences linearity performance, which is a critical measure of analog-to-digital converters (ADCs). Various placement techniques have been proposed to eliminate both systematic and random mismatches of capacitor pairs. However, a placement technique that eliminates capacitor mismatches may not result in good linearity performance for successive-approximation-register (SAR) ADCs because their linearity performance is related to the accuracy of their binary-weighted continued ratio. This paper addresses the critical problem of placement estimation based on ratio mismatch M, overall correlation coefficient L, and performance metrics. A low M and a high L value do not imply higher linearity performance. Therefore, we propose a partition-centering-based symmetry placement algorithm for the layout considering parasitic capacitance matching. The experimental results show that the proposed placement approach can achieve higher linearity performance and a shorter placement generation time compared with the conventional approach.Index Terms-Analog placement, capacitance ratio mismatch, spatial correlation coefficient, unit capacitor array placement, successive-approximation-register (SAR) ADC, binary-weighted continued ratio.