Developments in integrated smart sensors

An integrated smart sensor (ISS) can be defined as a chip that contains the functions of sensing, signal conditioning, AD conversion and a bus output. It may also have on-chip calibration and self-test. This paper concentrates on the standardization of the output interface using on-chip AD conversion, calibration and bus output. First, it is shown how indirect AD-conversion techniques yield simple circuits which can easily coexist with the sensor on one chip. Sigma-delta conversion is a good example. Second, calibration methods are described for analog and digital sensor output signals. Finally, the use of two simple busses is described, the I 2C bus and the IS 2 bus. The required bus interfaces are relatively simple and can be integrated with sensors in bipolar as well as in CMOS processes.