An on-chip integrated auto-tuned hybrid current-sensor for high-frequency low-power dc-dc converters

This paper introduces an on-chip implemented self-tuning current sensing circuit for integrated dc-dc converters. The circuit eliminates the problems of traditional sensing solutions related to relatively high power consumption and/or inaccurate current measurement. To accurately measure the inductor current at high switching frequencies while maintaining low power consumption, this circuit combines RC-filter and senseFET based current measurements and utilizes a novel 2-point high under-sampling rate technique for self-calibration. The new sensor is implemented as a part of an on-chip integrated 350 mW peak CPM controlled dc-dc converter operating at 4 MHz. The experimental results show that, compared to conventional senseFET implementation, the self-tuning circuit has about 20 times lower power consumption and eliminates the low-accuracy problem of RC-based methods.