Automated Design of a 13.56 MHz 19 μW Passive Rectifier With 72% Efficiency Under 10 μA load

A three-stage Greinacher rectifier is designed using ultra-low-leakage CMOS diodes and characterized at 13.56 MHz for a 1 Vpp sinusoidal input and a 10 mu A load current in 250 nm CMOS bulk technology. The measured dc output voltage is 1.9 V with 72% power conversion efficiency providing a 19 mu W output power. This ultra-low-power and high-efficiency ac/dc power converter with 0.13 mm(2) chip area can be used with RF energy harvesters to power implantable or wearable biomedical devices in body sensor networks. The automated design optimization methodology using a gradient method and foundry models is presented and discussed. The measured performances are presented for various frequencies, load currents, and input voltages. The robustness against process and temperature variations is studied through temperature measurements and corner simulations.