A CMOS Smart Temperature and Humidity Sensor with Combined Readout

Sensors

Clemens Eder¹  Virgilio Valente¹  Nick Donaldson² 

[1] Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, UK; E-Mails:;Department of Medical Physics and Bioengineering, University College London, Malet Place, WC1E 6BT, UK; E-Mail:

关键词: capacitive sensor;    humidity measurement;    microelectronic implants;    oscillator;    on-chip sensor;    temperature sensor;   

DOI  :  10.3390/s140917192

来源: mdpi

【 摘 要 】

A fully-integrated complementary metal-oxide semiconductor (CMOS) sensor for combined temperature and humidity measurements is presented. The main purpose of the device is to monitor the hermeticity of micro-packages for implanted integrated circuits and to ensure their safe operation by monitoring the operating temperature and humidity on-chip. The smart sensor has two modes of operation, in which either the temperature or humidity is converted into a digital code representing a frequency ratio between two oscillators. This ratio is determined by the ratios of the timing capacitances and bias currents in both oscillators. The reference oscillator is biased by a current whose temperature dependency is complementary to the proportional to absolute temperature (PTAT) current. For the temperature measurement, this results in an exceptional normalized sensitivity of about 0.77%/°C at the accepted expense of reduced linearity. The humidity sensor is a capacitor, whose value varies linearly with relative humidity (RH) with a normalized sensitivity of 0.055%/% RH. For comparison, two versions of the humidity sensor with an area of either 0.2 mm² or 1.2 mm² were fabricated in a commercial 0.18 μm CMOS process. The on-chip readout electronics operate from a 5 V power supply and consume a current of approximately 85 μA.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.