Automotive hybrid voltage regulator design with adaptive LDO dropout using load-sense technique
A switching converter (DC-DC) cascaded with parallel low dropout regulators (LDO) gives the best trade off in terms of high system efficiency and low output ripple for automotive Power Management ICs (PMIC). The minimum DC-DC output voltage is dependent on the highest LDO output and its corresponding dropout voltage. An adaptive LDO dropout technique based on Maximum Load Current Selector (MLCS) circuit has been proposed to improve the moderate and light load system efficiency of the cascaded DC-DC and multiple LDO combination. The input currents to the MLCS circuit is provided by current scaler circuit. The proposed circuit has been designed in AMS 0.35 m High-Voltage CMOS process and simulated across wide supply voltage (6V to 18V), wide load range (2mA to 300mA) and wide temperature range (-40°C to 150°C) to meet the automotive requirements. The adaptive dropout scheme works for any output voltage and load current of the LDOs. The overall system efficiency is improved by about 3% to 10% with minimal overhead (<; 2%) in terms of area compared to conventional fixed dropout architecture.