Rainbow Electronics MAX1623 - Manual

MAX1623
3A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
________________________________________________________________ Maxim Integrated Products 1
EVALUATION KIT MANUAL
AVAILABLE
General Description
The MAX1623 switch-mode buck regulator with syn-
chronous rectification provides local CPU and bus-ter-
mination power in notebook and desktop computers.
An internal 55m
Ω (typ), 3A PMOS power switch and
60m
Ω (typ), 3A NMOS synchronous-rectifier switch
deliver continuous load currents up to 3A from a 5V
supply with 95% typical efficiency. Output accuracy is
±1%, including line and load regulation.
The MAX1623 features constant-off-time, current-mode
pulse-width-modulation (PWM) control with switching
frequencies as high as 350kHz. An external resistor at
the TOFF pin sets the off-time, allowing optimum design
flexibility in terms of switching frequency, output switch-
ing noise, and inductor size. This device is available in
a space-saving 20-pin SSOP package.
________________________Applications
5V to 3.3V Conversion
Notebook Computer CPU I/O Supply
Desktop Computer Bus-Termination Supply
CPU Daughter Card Supply
DSP Supply
____________________________Features
♦ ±1% Output Accuracy, Including Line and Load
Regulation
♦ 94% Efficiency
♦ Internal Switches
55m Ω PMOS Power Switch
60m
Ω NMOS Synchronous-Rectifier Switch
♦ Guaranteed 3A Load Capability
♦ Minimal External Components
♦ Pin-Selectable Fixed 3.3V, 2.5V, or
Adjustable (1.1V to 3.8V) Output Voltage
♦ 4.5V to 5.5V Input Voltage Range
♦ 400µA (typ) Supply Current
♦ <1µA Shutdown Supply Current
♦ Constant-Off-Time PWM Operation
♦ Switching Frequencies Up to 350kHz
♦ Idle Mode™ Operation at Light Loads
♦ Thermal Shutdown Protection
♦ Available in 20-Pin SSOP
20
19
18
17
16
15
14
13
1
2
3
4
5
6
7
8
LX
PGND
LX
PGND IN
LX
IN
LX
TOP VIEW
LX
PGND
V CC
COMP FBSEL
IN
LX
12
11
9
10
REF
GND FB
TOFF
MAX1623
SSOP
SHDN
Pin Configuration
5V
INPUT
MAX1623
2.5V
OUTPUT
IN LX
PGND
GND
FB
REF COMP
FBSEL
V CC
TOFF
SHDN
Typical Operating Circuit
19-1436; Rev 2; 3/02
PART
MAX1623EAP -40°C to +85°C
TEMP RANGE PIN-PACKAGE
20 SSOP
Ordering Information
Idle Mode is a trademark of Maxim Integrated Products.
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.