MAX8743 Datasheet, PDF (1/27 Pages) Maxim Integrated Products – Dual, High-Efficiency, Step-Down Controller with High Impedance in Shutdown

19-3318; Rev 0; 6/04
Dual, High-Efficiency, Step-Down
Controller with High Impedance in Shutdown
General Description
The MAX8743 is a dual pulse-width modulation (PWM)
controller configured for step-down (buck) topologies
that provides the high efficiency, excellent transient
response, and high DC output accuracy necessary for
stepping down high-voltage batteries to generate low-
voltage chipset and RAM power supplies in notebook
computers. The CS_ inputs can be used with low-side
sense resistors to provide accurate current limits or can
be connected to LX_, using low-side MOSFETs as cur-
rent-sense elements. High output impedance in shut-
down eliminates negative output voltages, saving the
cost of a Schottky diode at the output.
The on-demand PWM controllers are free running, con-
stant on-time with input feed-forward. This configuration
provides ultra-fast transient response, wide input-output
differential range, low supply current, and tight load-reg-
ulation characteristics. The MAX8743 is simple and easy
to compensate.
Single-stage buck conversion allows the MAX8743 to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the 5V system supply instead of the bat-
tery at a higher switching frequency) allows the minimum
possible physical size.
The MAX8743 is intended for generating chipset, DRAM,
CPU I/O, or other low-voltage supplies down to 1V. The
MAX8743 is available in 28-pin QSOP and 36-pin thin
QFN packages.
Applications
Notebook Computers
CPU Core Supplies
Chipset/RAM Supplies as Low as 1V
1.8V and 2.5V I/O Supplies
Pin Configurations appear at end of data sheet.
Quick-PWM and Dual Mode are trademarks of Maxim Integrated
Products, Inc.
Features
♦ Ultra-High Efficiency
♦ Accurate Current-Limit Option
♦ Quick-PWM™ with 100ns Load-Step Response
♦ 1% V_OUT Accuracy over Line and Load
♦ High Output Impedance in Shutdown
♦ Dual Mode™ Fixed 1.8V/1.5V/Adj or 2.5V/Adj Outputs
♦ Adjustable 1V to 5.5V Output Range
♦ 2V to 28V Battery Input Range
♦ 200kHz/300kHz/420kHz/540kHz Nominal Switching
Frequency
♦ Adjustable Overvoltage Protection
♦ 1.7ms Digital Soft-Start
♦ Drives Large Synchronous-Rectifier FETs
♦ Power-Good Window Comparator
♦ 2V ±1% Reference Output
Ordering Information
PART
MAX8743EEI
MAX8743ETX
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
36 Thin QFN
6mm x 6mm
Minimal Operating Circuit
5V INPUT
OUTPUT1
1.8V
V_DD
V+
V_CC
UVP
ILIM1 OVP
ILIM2
ON1
ON2
BST1 BST2
DH1 DH2
LX1
LX2
DL1
DL2
TON
CS1
OUT1
PGOOD
REF
CS2
OUT2
SKIP
FB1
FB2
GND
BATTERY
4.5V TO 28V
MAX8743EEI
OUTPUT2
2.5V
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.