General Description

The RT8228A 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 RT8228A 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 and enter diode emulation mode at

light load condition. The buck conversion allows this device

to directly step down high voltage batteries at the highest

possible efficiency. The Audio Skipping Mode (ASM)

setting maintains the switching frequency above 25kHz,

which eliminates noise in audio applications. The RT8228A

is intended for CPU core, chipset, DRAM, or other low

voltage supplies as low as 0.5V. The RT8228A is available

in a WQFN-12L 2x2 package.

Applications

? Notebook Computers

? CPU Core Supply

? Chipset/RAM Supply as Low as 0.5V

? Generic DC/DC Power Regulator

Features

? Built in 1 0.5V Reference Voltage

? Adjustable 0.5V to 3.3V Output Range

? Quick Load Step Response within 100ns

? 4700ppm/°C Programmable Current Limit by Low

Side RDS(ON) Sensing

? 4.5V to 26V Battery Input Range

? Resistor Programmable Frequency

? Internal Ramp Current Limit Soft-Start Control

? Drives Large Synchronous Rectifier FETs

? Integrated Boost Switch

? Over/Under Voltage Protection

? Thermal Shutdown

? Power Good Indicator

? RoHS Compliant and Halogen Free