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3A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
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 55mΩ (typ), 3A PMOS power switch and
60mΩ (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.
____________________________Features
o
±1% Output Accuracy, Including Line and Load
Regulation
o
94% Efficiency
o
Internal Switches
55mΩ PMOS Power Switch
60mΩ NMOS Synchronous-Rectifier Switch
o
Guaranteed 3A Load Capability
o
Minimal External Components
o
Pin-Selectable Fixed 3.3V, 2.5V, or
Adjustable (1.1V to 3.8V) Output Voltage
o
+4.5V to +5.5V Input Voltage Range
o
400µA (typ) Supply Current
o
<1µA Shutdown Supply Current
o
o
o
o
o
Constant-Off-Time PWM Operation
Switching Frequencies Up to 350kHz
Idle Mode™ Operation at Light Loads
Thermal Shutdown Protection
Available in 20-Pin SSOP
MAX1623
________________________Applications
5V to 3.3V Conversion
Notebook Computer CPU I/O Supply
Desktop Computer Bus-Termination Supply
CPU Daughter Card Supply
DSP Supply
Ordering Information
PART
MAX1623EAP
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
20 SSOP
Typical Operating Circuit
TOP VIEW
+5V
INPUT
+2.5V
OUTPUT
IN
LX
Pin Configuration
LX 1
IN 2
20 LX
19 PGND
18 LX
17 PGND
MAX1623
LX 3
V
CC
FBSEL
SHDN
TOFF
COMP
FB
GND
REF
PGND
IN 4
LX 5
IN 6
SHDN 7
FBSEL 8
TOFF 9
FB 10
MAX1623
16 LX
15 PGND
14 V
CC
13 COMP
12 REF
11 GND
SSOP
Idle Mode is a trademark of Maxim Integrated Products.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
