The RT8202/A/B PWM controller provides high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high voltage batteries to generate low voltage CPU core, I/O, and chipset RAM supplies in notebook computers. The constant on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns “ instant-on ” response to load transients while maintaining a relatively constant switching frequency. The RT8202/A/B achieves high efficiency at a reduced cost by eliminating the current sense resistor found in traditional current mode PWMs. Efficiency is further enhanced by its ability to drive very large synchronous rectifier MOSFETs. The buck conversion allows this device to directly step down high voltage batteries for the highest possible efficiency. The RT8202/A/B is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.75V. RT8202 is available in WQFN-16L 4×4, RT8202A is available in WQFN-16L 3×3 and RT8202B is available in WQFN-14L 3.5×3.5 packages.