A high temperature micropower capacitive pressure sensor interface circuit

A pressure sensor interface circuit featuring micropower consumption is presented. The sensitivity to leakage currents has been reduced, allowing operation at high temperature. Special attention has been paid to minimise aliasing in the sampled interface. An optimal combination of contradictory requirements on power consumption, temperature range and sampling speed was obtained by a very careful system design and optimisation. The circuit converts a sensor capacitance variation of +/- 5pF into an 11 bit output word at a 2Hz rate. This resolution is guaranteed in the -40 degrees C to 100 degrees C temperature range. It may slowly decay above 100 degrees C but ensures at least 5 bit at 130 degrees C. The power consumption at room temperature is smaller than 2 mu A from a 2.4V to 4V battery.