Programmable mixed-voltage sensor readout circuit and bus interface with built-in self-test

As integrated sensors and microactuators are combined with embedded microcontrollers to form microsystems, there is an increasing need for highly-accurate interface circuits to provide the transducers with bus compatibility, programmable control, and self-test. Several readout circuits for capacitive sensors have been reported recently, including a generic interface that has been used extensively in a multi-element microsystem. This paper reports a bus-compatible interface chip that introduces several additional features, including a programmable mixed-signal mixed-voltage switched-capacitor (SC) read-out circuit with self-test and on-line calibration capabilities. This 4.5/spl times/4.5 mm/sup 2/ chip is in a 1 /spl mu/m n-well BiCMOS 2P/2M process with high-voltage CMOS, large-value resistor, and nonvolatile memory options.