A fully integrated CMOS-MEMS pressure sensor with on-chip /spl Delta/-/spl Sigma/ analog-to-digital converter

Piezoresistive CMOS-MEMS pressure sensor with ring oscillator readout including ΣΔ analog-to-digital converter on-chip

“…The relation between the applied pressure and stress is defined as (1) where p is the applied pressure, and the constants a and t are the width and the thickness of the diaphragm, while c depends on the geometrical and mechanical properties of the diaphragm material, in this case silicon. The diaphragm is amplifying the stress, and because of the piezoresistive property of silicon, it leads to a mobility change in the material.…”

“…Most of the sensors on the market can be divided into two groups; the piezoresistive solutions and, the most used solution today, the capacitive. To our knowledge a fully integrated CMOS-MEMS pressure sensor with on-chip A/D-converter has not been reported except from this work [1]. The proposed pressure sensor combines a Frequency Delta Sigma Modulator (FDSM) [2], [3] and a MEMS pressure controlled frequency modulator.…”

“…The scope of this paper is to characterize the pressure controlled oscillator and verify the functionality. Details on the other system components can be found in [1]. To maximize the stress/strain sensitivity, the position of the oscillator transistors relative to the diaphragm edge is critical.…”