A 51-ns Response-Time, Fully-Integrated, High-Side Current Sensor for a 40-V 6-A DC-DC Converter

A 130-nm CMOS high-side current sensor for peak-current DC-DC converters, operating with an input voltage up to 40 V is presented. A loop pre-biasing technique is used to prevent the proposed sense-FET-based current sensor from losing its linear behavior, thus achieving fast response time and, hence, allowing operation of the DC-DC converter with short minimum on-time. The proposed circuit also exploits a feedback resistance emulation technique for preventing the feedback loop to open during the blanking time. The current sensor has been integrated within a complete 40-V peak-current DC-DC buck converter that achieves 1-mV/A load regulation and 0.1-mV/V line regulation performances, even with a minimum on-time of 51 ns, with a peak efficiency of 92.5%.