A Speed- and Accuracy-Enhanced On-Chip Current Sensor with Local Shunt Feedback for Current-Mode Switching DC-DC Converters

A high-speed high-accuracy on-chip current sensor for current-mode switching dc-dc converters is presented in this paper. By employing local shunt feedback, the non-dominant pole in the current sensor is pushed to high frequency. Both speed and accuracy of the current sensor can then be improved simultaneously by consuming low quiescent current. The proposed current sensor for the buck converter is designed using a standard 0.35μm CMOS process. Results show that the proposed sensor achieves at least 95% sensing accuracy and ≪50ns settling time by consuming the quiescent current of 35μA. The sensor allows the current-mode buck converter to operate at switching frequencies up to 2MHz with a duty cycle down to 0.2.