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Número de pieza | LM2672M-12 | |
Descripción | SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features | |
Fabricantes | National Semiconductor | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de LM2672M-12 (archivo pdf) en la parte inferior de esta página. Total 22 Páginas | ||
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LM2672
SIMPLE SWITCHER® Power Converter High Efficiency
1A Step-Down Voltage Regulator with Features
General Description
The LM2672 series of regulators are monolithic integrated
circuits built with a LMDMOS process. These regulators pro-
vide all the active functions for a step-down (buck) switching
regulator, capable of driving a 1A load current with excellent
line and load regulation. These devices are available in fixed
output voltages of 3.3V, 5.0V, 12V, and an adjustable output
version.
Requiring a minimum number of external components, these
regulators are simple to use and include patented internal
frequency compensation (Patent Nos. 5,382,918 and
5,514,947), fixed frequency oscillator, external shutdown,
soft-start, and frequency synchronization.
The LM2672 series operates at a switching frequency of
260 kHz, thus allowing smaller sized filter components than
what would be needed with lower frequency switching regu-
lators. Because of its very high efficiency (>90%), the cop-
per traces on the printed circuit board are the only heat sink-
ing needed.
A family of standard inductors for use with the LM2672 are
available from several different manufacturers. This feature
greatly simplifies the design of switch-mode power supplies
using these advanced ICs. Also included in the datasheet
are selector guides for diodes and capacitors designed to
work in switch-mode power supplies.
Other features include a guaranteed ±1.5% tolerance on
output voltage within specified input voltages and output
load conditions, and ±10% on the oscillator frequency. Ex-
ternal shutdown is included, featuring typically 50 µA
stand-by current. The output switch includes current limiting,
as well as thermal shutdown for full protection under fault
conditions.
To simplify the LM2672 buck regulator design procedure,
there exists computer design software, LM267X Made
Simple version 1.0.
Features
n Efficiency up to 96%
n Available in SO-8 and 8-pin DIP packages
n Computer Design Software LM267X Made Simple
version 1.0
n Simple and easy to design with
n Requires only 5 external components
n Uses readily available standard inductors
n 3.3V, 5.0V, 12V, and adjustable output versions
n Adjustable version output voltage range: 1.21V to 37V
n ±1.5% max output voltage tolerance over line and load
conditions
n Guaranteed 1A output load current
n 0.25Ω DMOS Output Switch
n Wide input voltage range: 8V to 40V
n 260 kHz fixed frequency internal oscillator
n TTL shutdown capability, low power standby mode
n Soft-start and frequency synchronization
n Thermal shutdown and current limit protection
Typical Applications
n Simple High Efficiency (>90%) Step-Down (Buck)
Regulator
n Efficient Pre-Regulator for Linear Regulators
Typical Application (Fixed Output Voltage Versions)
SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation.
Windows® is a registered trademark of Microsoft Corporation.
© 1998 National Semiconductor Corporation DS012934
DS012934-1
www.national.com
1 page Typical Performance Characteristics (Continued)
Standby
Quiescent Current
ON/OFF Threshold
Voltage
ON/OFF Pin
Current (Sourcing)
DS012934-9
Switching Frequency
Feedback Pin
Bias Current
DS012934-10
DS012934-11
Peak Switch Current
DS012934-12
Dropout Voltage — 3.3V Option
DS012934-13
Dropout Voltage — 5.0V Option
DS012934-14
DS012934-15
DS012934-16
5 www.national.com
5 Page LM2672 Series Buck Regulator Design Procedure (Fixed Output) (Continued)
PROCEDURE (Fixed Output Voltage Version)
7. Frequency Synchronization (optional)
The LM2672 (oscillator) can be synchronized to run with an
external oscillator, using the sync pin (pin 3). By doing so, the
LM2672 can be operated at higher frequencies than the
standard frequency of 260 kHz. This allows for a reduction in
the size of the inductor and output capacitor.
As shown in the drawing below, a signal applied to a RC filter
at the sync pin causes the device to synchronize to the
frequency of that signal. For a signal with a peak-to-peak
amplitude of 3V or greater, a 1 kΩ resistor and a 100 pF
capacitor are suitable values.
EXAMPLE (Fixed Output Voltage Version)
7. Frequency Synchronization (optional)
For all applications, use a 1 kΩ resistor and a 100 pF capacitor
for the RC filter.
INDUCTOR VALUE SELECTION GUIDES (For Continuous Mode Operation)
FIGURE 4. LM2672-3.3
DS012934-29
FIGURE 6. LM2672-12
DS012934-31
FIGURE 5. LM2672-5.0
DS012934-30
11
DS012934-32
FIGURE 7. LM2672-ADJ
www.national.com
11 Page |
Páginas | Total 22 Páginas | |
PDF Descargar | [ Datasheet LM2672M-12.PDF ] |
Número de pieza | Descripción | Fabricantes |
LM2672M-12 | SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features | National Semiconductor |
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