NSC LM2671M-3.3, LM2671M-12, LM2671N-ADJ, LM2671N-5.0, LM2671N-12 Datasheet
...
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 provide all the active functions for a step-down (buck) switching
regulator, capable of driving a 500mA load current with excellent line and load regulation. These devices are available
in fixed output voltages of3.3V, 5.0V, 12V, and an adjustable
output version.
Requiring a minimumnumberofexternal 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 regulators. Because of its very high efficiency (
per traces on the printed circuit board are the only heat sinking 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
output voltage within specified input voltages and output
load conditions, and
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.
±
10%on the oscillator frequency. Ex-
>
90%), the cop-
±
1.5%tolerance on
To simplify the LM2671 buck regulator design procedure,
there exists computer design software,
Simple
.
LM267X Made
Features
n Efficiency up to 96
n Available in SO-8 and 8-pin DIP packages
n Computer Design Software
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 0.25Ω 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
%
LM267X Made Simple
Typical Applications
n Simple High Efficiency (>90%) Step-Down (Buck)
Regulator
n Efficient Pre-Regulator for Linear Regulators
LM2671 SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage
Regulator with Features
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
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 45V
ON/OFF Pin Voltage
Switch Voltage to Ground −1V
Boost Pin Voltage V
Feedback Pin Voltage −0.3V ≤ V
ESD Susceptibility
Human Body Model (Note 2) 2 kV
Power Dissipation Internally Limited
−0.1V ≤ VSH≤ 6V
+8V
SW
≤ 14V
FB
Storage Temperature Range −65˚C to +150˚C
Lead Temperature
M Package
Vapor Phase (60s) +215˚C
Infrared (15s) +220˚C
N Package (Soldering, 10s) +260˚C
Maximum Junction Temperature +150˚C
Operating Ratings
Supply Voltage 6.5V to 40V
Temperature Range −40˚C ≤ T
≤ +125˚C
J
Electrical Characteristics Specifications with standard type face are for T
face apply over full Operating Temperature Range.
=
25˚C, and those in bold type
J
LM2671-3.3
Symbol Parameter Conditions Typical Min Max Units
(Note 4) (Note 5) (Note 5)
SYSTEM PARAMETERS Test Circuit
V
V
Output Voltage V
OUT
Output Voltage V
OUT
η Efficiency V
Figure 2
=
8V to 40V, I
IN
=
6.5V to 40V, I
IN
=
12V, I
IN
(Note 3)
=
20 mA to 500 mA 3.3 3.251/3.201 3.350/3.399 V
LOAD
=
20 mA to 250 mA 3.3 3.251/3.201 3.350/3.399 V
LOAD
=
500 mA 86
LOAD
%
LM2671-5.0
Symbol Parameter Conditions Typical Min Max Units
(Note 4) (Note 5) (Note 5)
SYSTEM PARAMETERS Test Circuit
V
V
Output Voltage V
OUT
Output Voltage V
OUT
η Efficiency V
Figure 2
=
8V to 40V, I
IN
=
6.5V to 40V, I
IN
=
12V, I
IN
(Note 3)
=
20 mA to 500 mA 5.0 4.925/4.850 5.075/5.150 V
LOAD
=
20 mA to 250 mA 5.0 4.925/4.850 5.075/5.150 V
LOAD
=
500 mA 90
LOAD
%
LM2671-12
Symbol Parameter Conditions Typical Min Max Units
(Note 4) (Note 5) (Note 5)
SYSTEM PARAMETERS Test Circuit
V
Output Voltage V
OUT
η Efficiency V
=
15V to 40V, I
IN
=
24V, I
IN
Figure 2
LOAD
(Note 3)
=
20 mA to 500 mA 12 11.82/11.64 12.18/12.36 V
LOAD
=
500 mA 94
%
LM2671-ADJ
Symbol Parameter Conditions Typ Min Max Units
(Note 4) (Note 5) (Note 5)
SYSTEM PARAMETERS Test Circuit
V
V
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Feedback
FB
Voltage
Feedback
FB
Voltage
Figure 3
=
V
8V to 40V, I
IN
Programmed for 5V
V
OUT
(see Circuit of
=
V
6.5V to 40V, I
IN
Programmed for 5V
V
OUT
(see Circuit of
(Note 3)
LOAD
Figure 3
LOAD
Figure 3
=
20 mA to 500 mA
)
=
20 mA to 250 mA
)
1.210 1.192/1.174 1.228/1.246 V
1.210 1.192/1.174 1.228/1.246 V
LM2671-ADJ (Continued)
Symbol Parameter Conditions Typ Min Max Units
(Note 4) (Note 5) (Note 5)
SYSTEM PARAMETERS Test Circuit
η Efficiency V
Figure 3
(Note 3)
=
12V, I
IN
=
500 mA 90
LOAD
%
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for T
Range. Unless otherwise specified, V
and I
LOAD
=
100 mA.
IN
Symbol Parameters Conditions Typ Min Max Units
DEVICE PARAMETERS
I
Q
I
STBY
I
CL
I
L
R
f
O
Quiescent Current V
Standby Quiescent Current ON/OFF Pin=0V 50 100/150 µA
Current Limit 0.8 0.62/0.575 1.2/1.25 A
Output Leakage Current V
Switch On-Resistance I
DS(ON)
Oscillator Frequency Measured at Switch Pin 260 225 275 kHz
D Maximum Duty Cycle 95
Minimum Duty Cycle 0
I
BIAS
Feedback Bias V
Current ADJ Version Only
V
ON/OFF Pin 1.4 0.8 2.0 V
S/D
Voltage Thesholds
I
S/D
F
SYNC
V
V
I
SS
θ
JA
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see
the Electrical Characteristics.
Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 3: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator per-
formance. When the LM2671 is used as shown in
the Electrical Characteristics.
Note 4: Typical numbers are at 25˚C and represent the most likely norm.
Note 5: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%pro-
duction tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 6: Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will
lower thermal resistance further. See Application Information section in the application note accompanying this datasheet and the thermal model in
Simple
ON/OFF Pin Current ON/OFF Pin=0V 20 737µA
Synchronization Frequency V
Synchronization Threshold
SYNC
Voltage
Soft-Start Voltage 0.63 0.53 0.73 V
SS
Soft-Start Current 4.5 1.5 6.9 µA
Thermal Resistance N Package, Junction to Ambient (Note 6) 95 ˚C/W
Figure 2
version 1.0 software.
=
25˚C, and those in bold type face apply over full Operating Temperature
J
=
12V for the 3.3V, 5V, and Adjustable versions and V
=
FEEDBACK
8V 2.5 3.6 mA
For 3.3V, 5.0V, and ADJ Versions
V
FEEDBACK
=
15V 2.5 mA
For 12V Versions
=
40V, ON/OFF Pin=0V
IN
=
V
SWITCH
V
SWITCH
SWITCH
FEEDBACK
SYNC
0V
=
−1V, ON/OFF Pin=0V
=
500 mA 0.25 0.40/0.60 Ω
=
1.3V 85 nA
=
3.5V, 50%duty cycle 400 kHz
M Package, Junction to Ambient (Note 6) 105
and
Figure 3
test circuits, system performance will be as specified by the system parameters section of
=
24V for the 12V version,
IN
125µA
615mA
%
%
1.4 V
LM267X Made
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Connection Diagram
Typical Performance Characteristics
8-Lead Package
Top View
DS100042-2
For Surface Mount Package
Order Number
LM2671M-3.3, LM2671M-5.0,
LM2671M-12 or LM2671M-ADJ
See NSC Package Number M08A
For DIP Package
Order Number
LM2671N-3.3, LM2671N-5.0,
LM2671N-12 or LM2671N-ADJ
See NSC Package Number N08E
Normalized
Output Voltage
Efficiency
DS100042-3
DS100042-5
Line Regulation
DS100042-4
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Typical Performance Characteristics (Continued)
Drain-to-Source
Resistance
Operating
Quiescent Current
Standby
Quiescent Current
Switch Current Limit
DS100042-7
DS100042-6
DS100042-8
ON/OFF Threshold
Voltage
ON/OFF Pin
Current (Sourcing)
DS100042-9
DS100042-11
DS100042-10
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Typical Performance Characteristics (Continued)
Switching Frequency
Peak Switch Current
Dropout Voltage—3.3V Option
Feedback Pin
Bias Current
DS100042-12
DS100042-13
DS100042-14
Dropout Voltage—5.0V Option
DS100042-15
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DS100042-16
Block Diagram
* Patent Number 5,514,947
†
Patent Number 5,382,918
FIGURE 1.
Typical Performance Characteristics
Continuous Mode Switching Waveforms
=
V
20V, V
IN
L=100 µH, C
A: VSWPin Voltage, 10 V/div.
B: Inductor Current, 0.2 A/div
C: Output Ripple Voltage, 50 mV/div AC-Coupled
Horizontal Time Base: 1 µs/div
OUT
OUT
=
5V, I
=
100 µF, C
LOAD
=
500 mA
ESR=0.1Ω
OUT
DS100042-18
(Circuit of
A: VSWPin Voltage, 10 V/div.
B: Inductor Current, 0.5 A/div
C: Output Ripple Voltage, 20 mV/div AC-Coupled
Figure 2
)
Discontinuous Mode Switching Waveforms
=
V
IN
L=15 µH, C
20V, V
OUT
=
5V, I
OUT
=
68 µF (2x), C
LOAD
Horizontal Time Base: 1 µs/div
=
300 mA
ESR=25 mΩ
OUT
DS100042-17
DS100042-19
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