A High Temperature Micropower Capacitive Pressure Sensor Interface Circuit

A pressure sensor interface circuit featuring micropower consumptionis presented. The sensitivity to leakage currents has been reduced, allowingoperation at high temperature. Special attention has been paid to minimisealiasing in the sampled interface. An optimal combination of contradictoryrequirements on power consumption, temperature range and sampling speed wasobtained by a very careful system design and optimisation. The circuitconverts a sensor capacitance variation of ±5pF into an 11 bit outputword at a 2Hz rate. This resolution is guaranteed in the –40°C to100°C temperature range. It may slowly decay above 100°C but ensuresat least 5 bit at 130°C. The power consumption at room temperature issmaller than 2µA from a 2.4V to 4V battery.