A Wide Range Current Sensing Technique for Integrated DC-DC Converters

This work presents an on-chip ultra-low power, resistorless current sensor for energy harvesting systems. The proposed current sensor uses a sensing MOSFET in parallel with the PMOS power switch of a DC-DC boost converter and a low-complexity current-to-frequency converter to sense the average current of the battery connected at the output of the converter. The proposed topology is designed and simulated in XFAB XH018 CMOS process. The simulation results provide current sensing results with high accuracy, for current values as low as 300 uA and for converter switching frequencies up to 500 kHz. The maximum linearity error is calculated at 4.88%. The power consumption of the proposed current sensor is 1.57 uA at 2 V supply voltage (output battery voltage).