Enhanced SAR ADC energy efficiency from the early reset merged capacitor switching algorithm

Abstract

The early reset merged capacitor switching algorithm (EMCS) is proposed as an energy reducing switching technique for a binary weighted, capacitive successive approximation (SAR) analog to digital converter (ADC). The method uses the merged capacitor switching (MCS) architecture and optimizes the use of the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CM</sub> level during the SAR conversion. This algorithm can reduce switching power by over 12% with no additional DAC driver activity when compared to the MCS scheme. The MCS and EMCS approaches are analyzed mathematically and the EMCS energy consumption is shown to be lower than or equal to that of the MCS technique for every digital code. Static linearity improvements for this structure are also shown with the integral non-linearity (INL) reducing by a factor of two due to the utilization of the MCS three level DAC. The EMCS implementation methodology is also described.