A 0.5 V, 40nW voltage reference for WBAN devices

For WBAN (Wireless Body area network) devices, low supply voltage and high accuracy reference can reduce the power consumption of the whole circuit and prolong the battery life. This paper presents a 40nW, 0.5V supply voltage and 0.24V output reference for WBAN devices. The emitter-base voltage of a PNP transistor is divided by the switch capacitor circuit to obtain the low output reference. The resistor-less PTAT (proportional to absolute temperature) circuit and the low-voltage high PSRR (power supply rejection ratio) current source is used to improve the accuracy and line regulation performance of the reference. The proposed bandgap reference is implemented in 0.18μm standard CMOS process and has a total area of 0.058mm2. Test results show the minimum supply voltage is 0.5V. The line regulation is about 1.1mV/V in the supply voltage range of 0.5–0.9V. With 3-bit trimming, the TC (temperature coefficient) of 58 ppm/°C in the range of −25°C −85°C and the accuracy of 0.9% (3a) can be achieved.

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