Closed-Loop Temperature Control CMOS Integrated Circuit for Diagnostics and Self-calibration of Capacitive Humidity Sensors
A temperature control loop for capacitive humidity sensors has been developed in 0.35 µm CMOS technology and characterized with experimental lab measurements. The proposed circuit is employed for self-diagnostics of the humidity sensor as well as for auto-calibration, thanks to correlation between relative humidity and temperature. An input Switched-Capacitor (SC) thermometer read-out circuit compares the measured temperature value with a setpoint while a SC PWM PI circuit drives a power n-MOS to deliver heat to the sensor. Measurements results summary is reported. The temperature loop accuracy is ±0.25 ℃ in a range from room temperature to 50 ℃, while consuming 0.9 mA from a single 3.3 V supply for the control and about 43 mW for delivering heating power.
KeywordsAuto-Diagnostics Capacitive humidity sensor Temperature control loop Self-Calibration
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