Power Reduction in Incremental ΔΣ ADCs Using a Capacitor Scaling Technique

Abstract

Incremental analog to digital converters (IADCs) are aimed at converting low frequency signals with high accuracy. The operational transconductance amplifiers (OTAs) used to implement the integrators are the dominant source of power consumption, since they must settle to a desired accuracy within a given clock period, by driving a capacitive load. Reducing the capacitor size correspondingly increases the thermal noise power which reduces the signal-to-noise ratio (SNR) of the ADC. In this paper, we introduce a capacitor scaling technique which exploits the uneven weightage of the IADC decimation filter on the output bit-stream of the IADC. The power consumption can be scaled down correspondingly but the noise power does not increase by the same extent, leading to greater energy efficiency. A second order feedforward IADC is simulated to demonstrate the idea, which achieves up to a 25% improvement in energy efficiency using the proposed scheme.