Design Of Monolithic Integrated Circuit For An Integrated MHP Gas Sensor Array

Micro-hotplate has many advantages, such as low power, CMOS-process-compatible, low size, and so on. The emergence of Micro-hotplate provides support to develop integrated gas sensor with MHP array. To achieve detecting mixed gas effectively, MHP gas sensor array deposit different gas sensitive material that has different optimum operating temperature. Therefor it is very important to control the temperature of each sensor independently.Aiming at the demand of integrated MHP gas sensor array, a monolithic scheme is put forward by considering temperature regulation independently, effect of temperature control and chip area. This scheme is proposed based on the test results of MHP’s heating performance and it contains four MHP, heating driver block and signal acquisition block. Through importing serial control signal to the heating driver circuit by MCU, the temperature of MHP can be regulated by adjusting the heating current. The temperature signal and gas sensitive material resistance signal can be collected by the signal acquisition circuit, which controlled by the MCU. The selectivity of gas sensor can be improved by realizing monolithic integration of MHP gas sensor array and the peripheral circuit. Also this can provide important reference to the design of portable gas detection instrument.The system circuit is designed and simulated by using HSPICE based on0.5μm mixed signal process. Through simulating, the feasibility of this scheme is validated. The module layout is designed by using Cadence Layout-Editor, basing on the design rule of digital and analog mixed-signal layout. The whole layout is designed and verified by following the method of layout optimization. The GDS Ⅱ file is submitted to the factory and the chip is made. The micro-hotplate is becoming suspended structure after etching by using MEMS process. Then the MCU program is designed and the function of chip is tested.The test results show that the heating driver circuit can realize temperature regulation of MHP independently. And the accuracy of heating current is about3%. The heating driver circuit also can realize the control of MHP array’s operation mode. When the four MHP work to the highest temperature, the total power dissipation is about150mW. The signal acquisition circuit can realize the collection of MHP temperature signal.