A low power capacitance to pulse width converter for integrated sensors

An interface circuit for integrated capacitive sensors with pulse width modulated output is presented. The circuit is based on an original architecture implementing offset and low frequency noise cancellation by means of chopper modulation. Electrical simulations, performed on a prototype designed using 0.32 mum/ 3.3 V CMOS devices, showed that a sensitivity to temperature lower than 10 ppm/degC with a power consumption of 66 muW can be obtained with this approach.