Rainbow-electronics MAX1623 User Manual

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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 (typ), 3A PMOS power switch and
60m(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 PMOS Power Switch
60m 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 ModeOperation 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
COMPFBSEL
IN
LX
12
11
9
10
REF
GNDFB
TOFF
MAX1623
SSOP
SHDN
Pin Configuration
5V
INPUT
MAX1623
2.5V
OUTPUT
IN LX
PGND
GND
FB
REFCOMP
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.
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Summary of Contents

Page 1 - AVAILABLE

MAX16233A, Low-Voltage, Step-Down Regulator withSynchronous Rectification and Internal Switches_______________________________________________________

Page 2 - ELECTRICAL CHARACTERISTICS

MAX16233A, Low-Voltage, Step-Down Regulator withSynchronous Rectification and Internal Switches10 ____________________________________________________

Page 3

Loop Stability Stable operation requires the right output filter capaci-tor. When choosing the output capacitor, ensure the fol-lowing conditions are

Page 4 - (Circuit of Figure 2, T

MAX16233A, Low-Voltage, Step-Down Regulator withSynchronous Rectification and Internal SwitchesSSOP.EPSMaxim cannot assume responsibility for use of a

Page 5 - MAX1623 TOC13

MAX16233A, Low-Voltage, Step-Down Regulator withSynchronous Rectification and Internal Switches2 _____________________________________________________

Page 6 - Pin Description

MAX1623_______________________________________________________________________________________ 33A, Low-Voltage, Step-Down Regulator withSynchronous R

Page 7 - Setting the Output Voltage

MAX16233A, Low-Voltage, Step-Down Regulator withSynchronous Rectification and Internal Switches4 _____________________________________________________

Page 8 - Integrator Amplifier (COMP)

MAX1623_______________________________________________________________________________________ 53A, Low-Voltage, Step-Down Regulator withSynchronous R

Page 9

MAX16233A, Low-Voltage, Step-Down Regulator withSynchronous Rectification and Internal Switches6 _____________________________________________________

Page 10 - Applications Information

MAX1623_______________________________________________________________________________________ 73A, Low-Voltage, Step-Down Regulator withSynchronous R

Page 11 - Circuit Layout and Grounding

MAX16233A, Low-Voltage, Step-Down Regulator withSynchronous Rectification and Internal Switches8 _____________________________________________________

Page 12 - Package Information

A high capacitor value maintains a constant averageoutput voltage but slows the loop response to changesin output voltage. A low capacitor value speed

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