A capacitance-to-frequency converters comparison for a frequency acquisition platform

This paper presents a comparison of the most widely used capacitance to frequency (CtoF) converters found in the bibliography with a newly concept of relaxation oscillator circuit redesigned for raw sensors conditioning applications. The goal of frequency acquisition systems is to condition and acquire some specific parameters in safety critical monitoring systems where other acquisition techniques (ADC) have demonstrated not to be so suitable. Besides, not only frequency acquisition techniques based on CtoF and frequency to code (FtoC) conversion present better performances in real time behavior, but also better electrical characteristics. Furthermore, these systems have wide input spectrum range, high wide dynamic range, providing easy multiplexing for multichannel applications. The whole system shapes a readout integrated circuit (ROIC) in an AMS 0.35μM ASIC with a total area of 780μM*890μM. In addition a ROIC test board and a raw sensor platform board have been designed to perform all the characterization tests.