1V relaxation oscillator with integrated voltage and current reference

This Letter presents a novel relaxation oscillator with integrated voltage and current reference circuit, which generates a 32 kHz clock reference with 1% accuracy and has total power consumption of 122 nW at 1 V. Its temperature coefficient (TC) is 104 ppm/°C with a temperature range of −40 to 100°C, and its supply voltage accuracy is 1.6%/V from 1 to 1.8 V. The proposed oscillator uses the voltage reference directly to compare with the charging capacitor voltage, and the charging current is derived from the voltage reference divided by one temperature-independent resistor. The advantages are that the accuracy of output frequency and TC can be trimmed simultaneously and independently. It is fabricated in 0.18 μm CMOS technology and occupies 0.059 mm including the voltage and current reference circuits.