Ratiometric Voltage-to-Frequency Converter for Long-Life Autonomous Portable Equipment

This paper presents a high performance 1.2 V–0.18 $\mu{\rm m}$ CMOS voltage-to-frequency converter (VFC) that can be used either in single or differential mode to digitize sensor readout signals in wireless sensor network applications. The proposed VFC works over the entire input range with output frequencies ranging between 0.1 and 1.0MHz, which allows the sensor node embedded microcontroller performing optimally the final digitalization Its operation is ratiometric, adding value to this device when used in battery operated systems. High linearity is achieved (0.015% linearity error) with low power consumption (80 $\mu{\rm W}$) over a temperature range of ${-}{40}$ to ${+}{\rm 120}^{\circ}{\rm C}$.