A 1S Direct-Battery-Attach Buck Voltage Regulator With 5-Stack Thin-Gate 22-nm FinFET CMOS Featuring Active Voltage Balancing and Cascaded Self-Turn-ON Drivers

1S Li-Ion battery platforms have largely been adopting on-board voltage regulators (VRs) switching at a few MHz or lower for high efficiency. However, large currents on board traces eventually undermine the end-to-end efficiency, while large passives limit system miniaturization. By integrating the VR in the package, the trace loss can be saved and the VR can switch at higher frequency with a smaller inductor with the same power budget, reducing the power-delivery footprint significantly. In addition, a bulky high-voltage device can be replaced by a series of low-voltage, thin-gate devices, enabling efficient, high-frequency switching operations due to the superior device figure of merit. The proposed 5-stack, thin-gate power stage can deliver a peak efficiency of 89.2% for a 3.8 V into 1.8-V out, with $10\times $ higher power density (~15 A/mm ² ), switching at up to $10\times $ higher frequency (40 MHz) using $4\times $ – $10\times $ lower inductance (10–100 nH) than state of the art. Cascaded self-timed drivers and soft-switching low-side drivers minimize complexity in driving ten individual power switches safely, over a wide 1S battery voltage range. The measurement shows that each device stays within a safe voltage range during on and off states, due to voltage-balancing controls and self-timed drivers.