LAUSR

A switching converter (dc–dc) cascaded with parallel low-dropout (LDO) regulators gives the best tradeoff in terms of high system efficiency and low output ripple for automotive power management ICs (PMICs). 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 circuit has been proposed to improve the moderate and light load system efficiency of the hybrid PMIC with dc–dc supplying three independent LDO regulators. The circuit has been fabricated in AMS 0.35- $\mu \text{m}$ high-voltage CMOS process and tested across wide supply voltage of 6–18 V, wide temperature range of −40 °C to 150 °C, and maximum load of 450 mA to meet the harsh automotive application requirements. The adaptive dropout circuit has minimal overhead (<2%) in terms of area compared to fixed dropout architectures and negligible current consumption overhead. The overall system efficiency improvement of about 3%–10% is achieved with adaptive dropout scheme as per the experimental results. The concept is independent of dc–dc and LDO architecture and can be extended to many system-on-a-chip-based power supplies with dc–dc and LDO combination.