MAX8643A_0709 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – 3A, 2MHz Step-Down Regulator with Integrated Switches

19-0767; Rev 1; 9/07
3A, 2MHz Step-Down Regulator
with Integrated Switches
General Description
The MAX8643A high-efficiency switching regulator
delivers 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,
making it ideal for on-board point-of-load and postregu-
lation applications. Total output error is less than ±1%
over load, line, and temperature.
The MAX8643A 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 MAX8643A 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 MAX8643A 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 MAX8643A offers programmable soft-start
time using one capacitor to reduce input inrush current.
The MAX8643A 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
Pin Configuration appears at end of data sheet.
Features
o Internal 37mΩ R_DSON MOSFETs
o Continuous 3A Output Current
o ±1% Output Accuracy Over Load, Line,
and Temperature
o Operates from 2.35V to 3.6V Supply
o Adjustable Output from 0.6V to (0.9 x V_IN)
o Soft-Start Reduces Inrush Supply Current
o 500kHz to 2MHz Adjustable Switching Frequency
o Compatible with Ceramic, Polymer, and
Electrolytic Output Capacitors
o VID-Selectable Output Voltages
0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, and 2.5V
o Fully Protected Against Overcurrent
and Overtemperature
o Safe-Start into Prebiased Output
o Sink/Source Current in DDR Applications
o Lead-Free, 24-Pin, 4mm x 4mm Thin QFN Package
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
PKG
CODE
MAX8643AETG+ -40°C to +85°C
+Denotes a 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
MAX8643A
EN
LX
VDD
OUT
CTL1
CTL2
FREQ
REFIN
SS
PGND
FB
COMP
OUTPUT
1.8V, 3A
VDD
PREBIAS
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.