Richtek RT8238A Manual

Single Synchronous Buck PWM Controller
General Description
The RT8238A 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 RT8238A 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 Audio Skipping Mode (ASM)
setting maintains the switching frequency above 25kHz,
which eliminates noise in audio applications. The buck
conversion allows this device to directly step down high
voltage batteries at the highest possible efficiency. The
RT8238A is intended for CPU core, chipset, DRAM, or
other low voltage supplies as low as 0.5V. The RT8238A
is available in a WQFN-12L 2x2 package.
Ordering Information
RT8238A
Package Type
QW : WQFN-12L 2x2 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Note :
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
©
Copyright 2014 Richtek Technology Corporation. All rights reserved.
DS8238A-07 January 2014
®
Features
Applications
Pin Configurations
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 R Sensing
DS(ON)
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
Notebook Computers
CPU Core Supply
Chipset/RAM Supply as Low as 0.5V
Generic DC/DC Power Regulator
(TOP VIEW)
12
LGATE
1
PHASE
2
UGATE
3
4
WQFN-12L 2x2
is a registered trademark of Richtek Technology Corporation.
RT8238A
11 10
PGOOD
9
GND
EN
8
13
MODE
7
5 6
www.richtek.com
1