Research On Design Of Automobile Used Signal Conditioning Chip For Full Bridge Piezoresistive Pressure Sensor

The silicon micromachined piezoresistive pressure sensors have been developed for more than 30 years. From the primary structure of silicon-cup to recent structure of silicon-box, the pressure sensors become more miniatured, more reliable, and broader applications have been found in many different fields especially in automotive electronics. Compared to traditional pressure sensors, micromachined pressure sensors are featured with high volume, small size, low cost which are the most important factors in automotive applications. This kind of pressure sensors, however, have higher temperature sensitivity, temperature compensation is therefore necessary.This thesis focuses on the design of signal conditioning circuit for piezoresistive pressure sensor. The key point of this chip is the design of Bandgap, PTAT (Proportional to Absolute Temperature) voltage and Amplifier. PTAT voltage compensates for the sensor's temperature effect which contains temperature coefficient sensitivity (TCS) and temperature coefficient offset (TCO). The pressure sensor's signal is then amplified to meet the required output. This chip also contains communication interface and memory function.This thesis explains the fundamental causes of temperature effect of piezoresistive pressure sensor, and introduces a new method for temperature compensation. On this basis, the signal conditioning circuit is designed. The basic principles of Bandgap, PTAT, Chopper amplifier and Switched Capacitor amplifier are discussed, and the corresponding circuits and the simulation results are also given for this design.Finally, this chip is used for signal conditioning of Wheatstone bridge piezoresistive pressure sensor. Samples are chosen for temperature test, and the results indicate that the accuracy is 1%~3% in the total temperature range, and it shows that the chip has achieved the expected demands.