PASTEL: Parasitic Matching-Driven Placement and Routing of Capacitor Arrays With Generalized Ratios in Charge-Redistribution SAR-ADCs

Abstract

The charge-redistribution data converter topology is constructed from an array of parallel-connected capacitors with a specific capacitor ratio, and is a fundamental component of successive approximation register (SAR)-analog-to-digital converter (ADC) architectures. This paper presents complementary placement and routing algorithms for such capacitor arrays with the goal of nonlinearity minimization in the target SAR-ADC architecture. Starting from a state-of-the-art static nonlinearity model and its accompanying placement method, generalizations are made for both binary- and nonbinary-weighted capacitor ratios. Taking the generalized nonlinearity model and capacitor routing complexity into consideration, an improved placement method was developed, augmented with a matching-based routing technique driven by routing length adjustment. Analytical results compare the new methodology to the state-of-the-art, achieving superior resolution, linearity, and area.