1.5 V Sub-mW CMOS Interface Circuit for Capacitive Sensor Applications in Ubiquitous Sensor Networks

• Published in: ETRI journal Vol. 30; no. 5; pp. 644 - 652
• Main Authors: Lee, Sung-Sik, Lee, Ah-Ra, Je, Chang-Han, Lee, Myung-Lae, Hwang, Gunn, Choi, Chang-Auck
• Format: Journal Article
• Language: Korean
• Published: 한국전자통신연구원 05.02.2008; ETRI
• Subjects: Low-power CMOS interface circuit; ubiquitous sensor network (USN); capacitive MEMS sensor; readout integrated circuit (ROIC)
• ISSN: 1225-6463

In this paper, a low-power CMOS interface circuit is designed and demonstrated for capacitive sensor applications, which is implemented using a standard 0.35-${\mu}m$ CMOS logic technology. To achieve low-power performance, the low-voltage capacitance-to-pulse-width converter based on a self-reset operation at a supply voltage of 1.5 V is designed and incorporated into a new interface circuit. Moreover, the external pulse signal for the reset operation is made unnecessary by the employment of the self-reset operation. At a low supply voltage of 1.5 V, the new circuit requires a total power consumption of 0.47 mW with ultra-low power dissipation of 157 ${\mu}W$ of the interface-circuit core. These results demonstrate that the new interface circuit with self-reset operation successfully reduces power consumption. In addition, a prototype wireless sensor-module with the proposed circuit is successfully implemented for practical applications. Consequently, the new CMOS interface circuit can be used for the sensor applications in ubiquitous sensor networks, where low-power performance is essential.