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LM2671 Datasheet

SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator

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September 1998
LM2671
SIMPLE SWITCHER® Power Converter High Efficiency
500mA Step-Down Voltage Regulator with Features
General Description
The LM2671 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 500mA load current with ex-
cellent 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 LM2671 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 LM2671 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 LM2671 buck regulator design procedure,
there exists computer design software, LM267X Made
Simple.
Features
n Efficiency up to 96%
n Available in SO-8 and 8-pin DIP packages
n Computer Design Software LM267X Made Simple
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 500mA output load current
n 0.25DMOS 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)
DS100042-1
SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation.
Windows® is a registered trademark of Microsoft Corporation.
© 1998 National Semiconductor Corporation DS100042
www.national.com


National Semiconductor Electronic Components Datasheet

LM2671 Datasheet

SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator

No Preview Available !

Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
ON/OFF Pin Voltage
Switch Voltage to Ground
Boost Pin Voltage
Feedback Pin Voltage
ESD Susceptibility
Human Body Model (Note 2)
Power Dissipation
45V
−0.1V VSH 6V
−1V
VSW + 8V
−0.3V VFB 14V
2 kV
Internally Limited
Storage Temperature Range
Lead Temperature
M Package
Vapor Phase (60s)
Infrared (15s)
N Package (Soldering, 10s)
Maximum Junction Temperature
Operating Ratings
Supply Voltage
Temperature Range
−65˚C to +150˚C
+215˚C
+220˚C
+260˚C
+150˚C
6.5V to 40V
−40˚C TJ +125˚C
Electrical Characteristics Specifications with standard type face are for TJ = 25˚C, and those in bold type
face apply over full Operating Temperature Range.
LM2671-3.3
Symbol
Parameter
Conditions
SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)
VOUT
VOUT
η
Output Voltage
Output Voltage
Efficiency
VIN = 8V to 40V, ILOAD = 20 mA to 500 mA
VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA
VIN = 12V, ILOAD = 500 mA
Typical
(Note 4)
Min
(Note 5)
Max
(Note 5)
Units
3.3 3.251/3.201 3.350/3.399 V
3.3 3.251/3.201 3.350/3.399 V
86 %
LM2671-5.0
Symbol
Parameter
Conditions
SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)
VOUT
VOUT
η
Output Voltage
Output Voltage
Efficiency
VIN = 8V to 40V, ILOAD = 20 mA to 500 mA
VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA
VIN = 12V, ILOAD = 500 mA
Typical
(Note 4)
Min
(Note 5)
Max
(Note 5)
Units
5.0 4.925/4.850 5.075/5.150 V
5.0 4.925/4.850 5.075/5.150 V
90 %
LM2671-12
Symbol
Parameter
Conditions
SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)
VOUT
η
Output Voltage
Efficiency
VIN = 15V to 40V, ILOAD = 20 mA to 500 mA
VIN = 24V, ILOAD = 500 mA
Typical
(Note 4)
Min
(Note 5)
Max
(Note 5)
Units
12 11.82/11.64 12.18/12.36 V
94 %
LM2671-ADJ
Symbol
Parameter
Conditions
SYSTEM PARAMETERS Test Circuit Figure 3 (Note 3)
VFB Feedback
Voltage
VIN = 8V to 40V, ILOAD = 20 mA to 500 mA
VOUT Programmed for 5V
(see Circuit of Figure 3)
VFB Feedback
Voltage
VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA
VOUT Programmed for 5V
(see Circuit of Figure 3)
Typ
(Note 4)
Min
(Note 5)
Max
(Note 5)
Units
1.210 1.192/1.174 1.228/1.246 V
1.210 1.192/1.174 1.228/1.246 V
www.national.com
2


Part Number LM2671
Description SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator
Maker National Semiconductor
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LM2671 Datasheet PDF






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