A New Chessboard Placement and Sizing Method for Capacitors in a Charge-Scaling DAC by Worst-Case Analysis of Nonlinearity

Charge scaling data converters include a binary-weighted capacitor array in their structure. New methods for the placement and sizing of capacitor arrays with increased ratio accuracy and improved converter linearity are presented in this paper. A new model of statistical variation is used, which takes into account both spatial correlation between devices and device area. This is combined with a novel analytical model for the linearity metrics of a charge scaling digital-to-analog converter. Minimizing the variance of the linearity metrics directs a new chessboard placement method for the capacitor array. Chessboard placement is shown to be superior to the state of the art in consideration of both random and systematic mismatch. The new analytical model is then used to develop a flow for capacitor array sizing.