A PVT Compensated Resistance to Frequency Converter for Sensor Array Read-Out

Abstract

This brief presents a PVT (process, voltage, temperature) compensated CMOS resistor to frequency read-out circuit for resistive sensing applications. Resistive sensing is used in different applications, such as olfactory sensing. An accurate read-out circuit is needed to detect the resistance values for on-chip sensor arrays. Existing techniques suffer from PVT variations and require a large silicon chip area. The proposed design offers a simple, accurate, PVT insensitive sensor read-out circuit where a closed-loop configuration, a switched capacitor resistor, operational amplifier integrator, and a voltage-controlled oscillator are used. The design is implemented and fabricated using TSMC 180 nm CMOS technology. The value for the measured sensor&#x2019;s resistance ranges between 10k and 100M <inline-formula> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> with an accuracy of 0.1&#x0025; while the chip area is <inline-formula> <tex-math notation="LaTeX">$0.0455{ {mm}}^{{2}}$ </tex-math></inline-formula> with <inline-formula> <tex-math notation="LaTeX">$98.1\mu {W}$ </tex-math></inline-formula> power consumption. Also, the settling time for the step resistance change is about <inline-formula> <tex-math notation="LaTeX">$2 \mu \text{s}$ </tex-math></inline-formula>.