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PDF MAX1623EAP Data sheet ( Hoja de datos )
| Número de pieza | MAX1623EAP | |
| Descripción | 3A / Low-Voltage / Step-Down Regulator with Synchronous Rectification and Internal Switches | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-1436; Rev 1; 9/99
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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.
________________________Applications
5V to 3.3V Conversion
Notebook Computer CPU I/O Supply
Desktop Computer Bus-Termination Supply
CPU Daughter Card Supply
DSP Supply
Typical Operating Circuit
____________________________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 Constant-Off-Time PWM Operation
o Switching Frequencies Up to 350kHz
o Idle Mode™ Operation at Light Loads
o Thermal Shutdown Protection
o Available in 20-Pin SSOP
PART
MAX1623EAP
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
20 SSOP
Pin Configuration
+5V
INPUT
IN LX
MAX1623
VCC
FBSEL
PGND
SHDN
FB
TOFF GND
COMP REF
+2.5V
OUTPUT
TOP VIEW
LX 1
IN 2
LX 3
IN 4
LX 5
IN 6
SHDN 7
FBSEL 8
TOFF 9
FB 10
MAX1623
20 LX
19 PGND
18 LX
17 PGND
16 LX
15 PGND
14 VCC
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.
1 page  
3A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
____________________________ Typical Operating Characteristics (continued)
(Circuit of Figure 2, TA = +25°C, unless otherwise noted.)
START-UP AND SHUTDOWN TRANSIENT
START-UP AND SHUTDOWN TRANSIENT
LOAD-TRANSIENT RESPONSE
(FBSEL = REF)
A
B
C
1ms/div
VIN = 5V, VOUT = 3.3V, ILOAD = 3A,
WAVEFORM AVERAGED
A: VOUT, 2V/div
B: IIN, 1A/div
C: VSHDN, 5V/div
A
B
C
1ms/div
VIN = 5V, VOUT = 3.3V, ILOAD = 2A,
WAVEFORM AVERAGED
A: VOUT, 2V/div
B: IIN, 1A/div
C: VSHDN, 5V/div
ILOAD
0 to 3A
VOUT
50mV
AC-COUPLED
f = 300kHz
20µs/div
LOAD-TRANSIENT RESPONSE
(FBSEL = REF)
ILOAD
0 to 2A
VOUT
50mV
AC-COUPLED
f = 300kHz
20µs/div
LINE-TRANSIENT RESPONSE
VIN = 4.5V
to 5.5V
AC-COUPLED
(1V/div)
VOUT = 3.3V
AC-COUPLED
IOUT = 1.5A
(20mV/div)
20µs/div
LINE-TRANSIENT RESPONSE
VIN = 4.5V
to 5.5V
AC-COUPLED
(1V/div)
VOUT = 3.3V
AC-COUPLED
IOUT = 100mA
(20mV/div)
20µs/div
_______________________________________________________________________________________ 5
5 Page 
3A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
Loop Stability
Stable operation requires the right output filter capaci-
tor. When choosing the output capacitor, ensure the fol-
lowing conditions are met:
C2 ≥ 80⋅ tOFF ⋅ VREF
VOUT
and
10mΩ ≤ RESR, C2 ≤ 50mΩ
Circuit Layout and Grounding
Good layout is necessary to achieve the intended out-
put power level, high efficiency, and low noise. Good
layout includes the use of a ground plane, appropriate
component placement, and correct routing of traces
using appropriate trace widths. For heatsinking purpos-
es, copper area connected at the IC should be evenly
distributed among the high-current pins.
1) Minimize high-current ground loops. Connect the
input capacitor’s ground, output capacitor’s
ground, and IC PGND together.
2) A ground plane is essential for optimum perfor-
mance. In most applications, the circuit will be
located on a multilayer board, and full use of the
four or more copper layers is recommended. Use
the top and bottom layers for interconnections and
the inner layers for an uninterrupted ground plane.
3) Place the LX node components as close together
as possible. This reduces resistive and switching
losses and confines noise due to ground induc-
tance.
4) Connect the input filter capacitor less than 10mm
away from IN. The connecting copper trace carries
large currents and must be at least 2mm wide,
preferably 5mm.
5) Connect GND directly to PGND at only one point
near the IC.
___________________Chip Information
TRANSISTOR COUNT: 1220
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX1623EAP.PDF ] | |
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