A 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m CMOS Voltage-to-Frequency Converter With Low Circuit Sensitivity

Abstract

A process, voltage and temperature insensitive resistor-to-frequency converter is proposed. This insensitivity is achieved by matching the current defining capacitor in a novel switched-capacitor (SC) voltage-to-current (V-I) converter with the integrating capacitor in a conventional relaxation oscillator. Implemented in 0.18 μm CMOS technology, the SC V-I converter together with the relaxation oscillator and voltage regulator occupies 0.45mm 2 . The proposed work has shown a sensitivity of 199.9 Hz/(μΩ/Ω) which is based on a center frequency of 125kHz. Testing with a commercial sensor, the sensor interface has demonstrated a sensitivity of 1.269 kHz/psi. The sensor interface consumes only 112.5 μW at 1.5V power supply. Therefore, it is suitable for Internet-of-Things applications.

A Highly Robust Interface Circuit for Resistive Sensors

“…This results in large and complex configurations and linearization techniques must be applied due to the intrinsic limitation in the dynamic range [2][3][4]. In contrast, quasi-digital converters, i.e., resistance-to-frequency [5,6], -period [7,8] or -duty-cycle [9] converters, are preferred if the resistance variations are very large. This converters not only provide a wider dynamic range but also simplify interfacing to digital systems, as no analog-to-digital converters (ADCs) are required [10,11].…”