Charge Redistribution Mitigation and Optimization for Sensor–ADC Interfacing in Low Cost Embedded Applications

Abstract

This paper proposes a cost-effective five-component discrete capacitive pre-charging circuit designed to mitigate charge redistribution effects in Analog-to-Digital Converter (ADC) inputs, particularly for low-cost embedded applications involving multiplexed high-output-resistance sources. The paper presents an analysis and experimental validation of this approach, comparing its performance against traditional methods like grounding or leaving unused multiplexer inputs floating. The proposed solution leverages external components (two capacitors and three switches) and multiplexer features to pre-charge ADC inputs to approximately half the reference voltage, which could be taken directly from the multiplexer supply rail, significantly reducing transient glitches and settling times. The experimental results demonstrate a clear improvement, achieving settling times up to 1.4 µs shorter than conventional approaches during specific multiplexer transitions. Component selection guidelines are outlined, including compensation capacitor sizing and transistor choice, addressing practical concerns such as charge injection effects. Despite certain experimental constraints noted during testing, the developed discrete pre-charging method consistently exhibited substantial performance gains. Our findings confirm that this practical, minimal-component strategy effectively addresses charge redistribution challenges, presenting an efficient solution for enhancing ADC input accuracy and response speed in resource-limited embedded sensor systems.

Keywords

• ADC interface
• capacitive precharging
• charge redistribution
• multiplexer
• embedded systems
• transient effects