A Highly Linear, AEC-Q100 Compliant Signal Conditioning IC for Automotive Piezo-Resistive Pressure Sensors

In this paper, the design of a signal conditioning analog front-end (AFE) IC for an automotive piezo-resistive type pressure sensor is presented. To improve the pressure-sensing accuracy and compensate for variations in the pressure sensor and signal conditioning IC, gauge factor calibration, digital automatic offset, and gain calibration are proposed and implemented with low power consumption. By using a high-resolution analog-to-digital converter and digital-to-analog converter, the digital automatic calibration circuit can guarantee linearity of output voltage with respect to pressure to within 0.5%. As the analog signal is converted to a digital signal, accuracy in the AFE IC improves. To improve the reliability in the automotive environment, over-voltage and reverse-voltage protection circuits are integrated with the electrostatic discharge protection circuit. Also, electromagnetic interference is reduced by using the proposed spread spectrum clock generator. The proposed design is implemented using 2P4M 0.35 μm CMOS technology with an active area of 1.94 mm × 1.94 mm. Full output ranges from 0.5 to 4.5 V. The ratiometricity error is within ±0.25% when the supply voltage is changed by ±10%. Current consumption is 4.7 mA from a 5 V supply. The output accuracy is within ±0.5% with respect to the PVT variations.