A temperature compensated CMOS ring oscillator for wireless sensing applications

This paper presents a CMOS voltage controlled ring oscillator (VCO) with temperature compensation circuit suitable for low-cost and low-power wireless sensing applications. To operate at low frequency, a control voltage generated by a CMOS bandgap reference (BGR) is described and the measurement results of the fabricated chips are presented. The output voltage of the reference is set by resistive subdivision. In order to achieve small area and low power consumption, n-well resistors are used. This design features a reference voltage of 1V. The chip is fabricated in AMS 0.35 μm CMOS process with an area of 0.032mm². Operating at 1.25V, the output frequency is within 200±l0kHz over the temperature range of -25°C to 80°C with power consumption of 810μW.