Voltage-to-frequency converter for low-power sensor interfaces

Abstract

This paper presents a low-power rail-to-rail temperature compensated voltage-to-frequency converter (VFC) which constitutes the last stage of a sensor read-out interface targeting portable applications, such as wireless sensor networks. Results for a 0.18 µm – 1.2 V CMOS VFC ASIC implementation show for an input range of (0 – 1.2 V) an output frequency range of (0.1 – 1.0 MHz), adequate to digitize the signal with the direct counting method in the sensor node microcontroller. The proposed VFC has a power consumption of 60 µW in normal operation, 35 nW in sleep mode, and it is temperature insensitive for a temperature range of (−40, 120 °C).