Low-Power Direct Resistive Sensor-to-Microcontroller Interfaces

Abstract

This paper analyzes the energy consumption of direct interface circuits where the data conversion of a resistive sensor is performed by a direct connection to a set of digital ports of a microcontroller ( $\mu \text{C}$ ). The causes of energy consumption as well as their relation to the measurement specifications in terms of uncertainty are analyzed. This analysis yields a tradeoff between energy consumption and measurement uncertainty, which sets a design procedure focused on achieving the lowest energy consumption for a given uncertainty and a measuring range. Together with this analysis, a novel experimental setup is proposed that allows one to measure the $\mu \text{C}$ ’s timer quantization uncertainty. An application example is shown where the design procedure is applied. The experimental results fairly fit the theoretical analysis, yielding only $5~\mu \text{J}$ to achieve nine effective number of bits (ENOB) in a measuring range from 1 to 1.38 $\text{k}\Omega $ . With the same ENOB, the energy is reduced to $1.9~\mu \text{J}$ when the measurement limits are changed to 100 and 138 $\text{k}\Omega $ .