MAX8643_0709 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – 3A, 2MHz Step-Down Regulator with Integrated Switches

19-3970; Rev 3; 9/07
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3A, 2MHz Step-Down Regulator
with Integrated Switches
General Description
The MAX8643 high-efficiency switching regulator deliv-
ers up to 3A load current at output voltages from 0.6V
to (0.9 x V_IN).The IC operates from 2.35V to 3.6V, mak-
ing it ideal for on-board point-of-load and postregula-
tion applications. Total output error is less than ±1%
over load, line, and temperature.
The MAX8643 features fixed-frequency PWM mode
operation with a switching frequency range of 500kHz
to 2MHz set by an external resistor. High-frequency
operation allows for an all-ceramic capacitor design.
The high operating frequency also allows for small-size
external components.
The low-resistance on-chip nMOS switches ensure high
efficiency at heavy loads while minimizing critical induc-
tances, making the layout a much simpler task with
respect to discrete solutions. Following a simple layout
and footprint ensures first-pass success in new designs.
The MAX8643 comes with a high-bandwidth (> 14MHz)
voltage-error amplifier. The voltage-mode control archi-
tecture and the voltage-error amplifier permit a type III
compensation scheme to be utilized to achieve maxi-
mum loop bandwidth, up to 20% of the switching fre-
quency. High loop bandwidth provides fast transient
response, resulting in less required output capacitance
and allowing for all-ceramic capacitor designs.
The MAX8643 provides two tri-state logic inputs to
select one of nine preset output voltages. The preset
output voltages allow customers to achieve ±1% out-
put-voltage accuracy without using expensive 0.1%
resistors. In addition, the output voltage can be set to
any customer value by either using two external resis-
tors at the feedback with 0.6V internal reference or
applying an external reference voltage to the REFIN
input. The MAX8643 offers programmable soft-start
time using one capacitor to reduce input inrush current.
The MAX8643 is available in a lead-free, 24-pin, 4mm x
4mm thin QFN package.
Applications
POLs
ASIC/CPU/DSP Core and I/O Voltages
DDR Power Supplies
Base-Station Power Supplies
Telecom and Networking Power Supplies
RAID Control Power Supplies
Features
♦ Internal 37mΩ R_DSON MOSFETs
♦ Continuous 3A Output Current
♦ ±1% Output Accuracy Over Load, Line,
and Temperature
♦ Operates from 2.35V to 3.6V Supply
♦ Adjustable Output from 0.6V to (0.9 x V_IN)
♦ Soft-Start Reduces Inrush Supply Current
♦ 500kHz to 2MHz Adjustable Switching Frequency
♦ Compatible with Ceramic, Polymer, and
Electrolytic Output Capacitors
♦ VID-Selectable Output Voltages
0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, and 2.5V
♦ Fully Protected Against Overcurrent
and Overtemperature
♦ Sink/Source Current in DDR Application
♦ Lead-Free, 24-Pin, 4mm x 4mm
Thin QFN Package
Ordering Information
PART
TEMP
RANGE
PIN-PACKAGE
PKG
CODE
MAX8643ETG+
-40°C to
+85°C
+Denotes lead-free package.
*EP = Exposed pad.
24 Thin QFN-EP*
4mm x 4mm
T2444-4
INPUT
2.4V, 3.6V
Typical Operating Circuit
IN
BST
MAX8643
EN
LX
VDD
OUT
CTL1
CTL2
FREQ
REFIN
SS
PGND
FB
COMP
OUTPUT
1.8V, 3A
VDD
Pin Configuration appears at end of data sheet.
PWRGD
GND
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.