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LM2576/LM2576HV Series SIMPLE SWITCHER(RM) 3A Step-Down Voltage Regulator
September 1996
LM2576/LM2576HV Series
SIMPLE SWITCHER É 3A Step-Down Voltage Regulator
General Description
The LM2576 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving 3A load with
excellent line and load regulation. These devices are avail-
able in fixed output voltages of 3.3V, 5V, 12V, 15V, and an
adjustable output version.
Requiring a minimum number of external components,
these regulators are simple to use and include internal fre-
quency compensation and a fixed-frequency oscillator.
The LM2576 series offers a high-efficiency replacement for
popular three-terminal linear regulators. It substantially re-
duces the size of the heat sink, and in some cases no heat
sink is required.
A standard series of inductors optimized for use with the
LM2576 are available from several different manufacturers.
This feature greatly simplifies the design of switch-mode
power supplies.
Other features include a guaranteed g 4% tolerance on out-
put voltage within specified input voltages and output load
conditions, and g 10% on the oscillator frequency. External
shutdown is included, featuring 50 m A (typical) standby cur-
rent. The output switch includes cycle-by-cycle current limit-
ing, as well as thermal shutdown for full protection under
fault conditions.
Features
Y 3.3V, 5V, 12V, 15V, and adjustable output versions
Y Adjustable version output voltage range,
1.23V to 37V (57V for HV version) g 4% max over
line and load conditions
Y Guaranteed 3A output current
Y Wide input voltage range, 40V up to 60V for
HV version
Y Requires only 4 external components
Y 52 kHz fixed frequency internal oscillator
Y TTL shutdown capability, low power standby mode
Y High efficiency
Y Uses readily available standard inductors
Y Thermal shutdown and current limit protection
Y P a Product Enhancement tested
Applications
Y Simple high-efficiency step-down (buck) regulator
Y Efficient pre-regulator for linear regulators
Y On-card switching regulators
Y Positive to negative converter (Buck-Boost)
Typical Application (Fixed Output Voltage Versions)
TL/H/11476±1
FIGURE 1
Block Diagram
3.3V R2 e 1.7k
5V, R2 e 3.1k
12V, R2 e 8.84k
15V, R2 e 11.3k
For ADJ. Version
R1 e Open, R2 e 0 X
TL/H/11476±2
Patent Pending
SIMPLE SWITCHER É is a registered trademark of National Semiconductor Corporation.
C 1996 National Semiconductor Corporation
TL/H/11476
RRD-B30M106/Printed in U. S. A.
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Maximum Supply Voltage
LM2576
Minimum ESD Rating
(C e 100 pF, R e 1.5 k X )
2 kV
Lead Temperature
(Soldering, 10 Seconds)
260 § C
45V
Maximum Junction Temperature
150 § C
L M2576HV
63V
ON/OFF Pin Input Voltage
b 0.3V s V s a V IN
Operating Ratings
Temperature Range
LM2576/LM2576HV
Output Voltage to Ground
(Steady State)
b 1V
b 40 § C s T J s a 125 § C
Power Dissipation
Internally Limited
Supply Voltage
LM2576
Storage Temperature Range
b 65 § Cto a 150 § C
40V
LM2576HV
60V
LM2576-3.3, LM2576HV-3.3
Electrical Characteristics Specifications with standard type face are for T J e 25 § C, and those with boldface
type apply over full Operating Temperature Range.
LM2576-3.3
Symbol
Parameter
Conditions
LM2576HV-3.3
Units
(Limits)
Limit
(Note 2)
Typ
SYSTEM PARAMETERS (Note 3) Test Circuit Figure2
V OUT
Output Voltage
V IN e 12V, I LOAD e 0.5A
3.3
V
Circuit of Figure2
3.234
V(Min)
3.366
V(Max)
V OUT
Output Voltage
6V s V IN s 40V, 0.5A s I LOAD s 3A
3.3
V
LM2576
Circuit of Figure2
3.168/3.135 V(Min)
3.432/3.465 V(Max)
V OUT
Output Voltage
6V s V IN s 60V, 0.5A s I LOAD s 3A
3.3
V
LM2576HV
Circuit of Figure2
3.168/3.135 V(Min)
3.450/3.482 V(Max)
h
Efficiency
V IN e 12V, I LOAD e 3A
75
%
LM2576-5.0, LM2576HV-5.0
Electrical Characteristics Specifications with standard type face are for T J e 25 § C, and those with boldface
type apply over full Operating Temperature Range.
LM2576-5.0
Symbol
Parameter
Conditions
LM2576HV-5.0
Units
(Limits)
Limit
(Note 2)
Typ
SYSTEM PARAMETERS (Note 3) Test Circuit Figure2
V OUT
Output Voltage
V IN e 12V, I LOAD e 0.5A
5.0
V
Circuit of Figure2
4.900
V(Min)
5.100
V(Max)
V OUT
Output Voltage
0.5A s I LOAD s 3A,
5.0
V
LM2576
8V s V IN s 40V
4.800/4.750
V(Min)
Circuit of Figure2
5.200/5.250
V(Max)
V OUT
Output Voltage
0.5A s I LOAD s 3A,
5.0
V
LM2576HV
8V s V IN s 60V
4.800/4.750
V(Min)
Circuit of Figure2
5.225/5.275
V(Max)
h
Efficiency
V IN e 12V, I LOAD e 3A
77
%
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2
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LM2576-12, LM2576HV-12
Electrical Characteristics Specifications with standard type face are for T J e 25 § C, and those with boldface
type apply over full Operating Temperature Range.
LM2576-12
Symbol
Parameter
Conditions
LM2576HV-12
Units
(Limits)
Limit
(Note 2)
Typ
SYSTEM PARAMETERS (Note 3) Test Circuit Figure2
V OUT
Output Voltage
V IN e 25V, I LOAD e 0.5A
12
V
Circuit of Figure2
11.76
V(Min)
12.24
V(Max)
V OUT
Output Voltage
0.5A s I LOAD s 3A,
12
V
LM2576
15V s V IN s 40V
11.52/11.40
V(Min)
Circuit of Figure2
12.48/12.60
V(Max)
V OUT
Output Voltage
0.5A s I LOAD s 3A,
12
V
LM2576HV
15V s V IN s 60V
11.52/11.40
V(Min)
Circuit of Figure2
12.54/12.66
V(Max)
h
Efficiency
V IN e 15V, I LOAD e 3A
88
%
LM2576-15, LM2576HV-15
Electrical Characteristics Specifications with standard type face are for T J e 25 § C, and those with boldface
type apply over full Operating Temperature Range.
LM2576-15
Symbol
Parameter
Conditions
LM2576HV-15
Units
Limit
(Note 2)
(Limits)
Typ
SYSTEM PARAMETERS (Note 3) Test Circuit Figure2
V OUT
Output Voltage
V IN e 25V, I LOAD e 0.5A
15
V
Circuit of Figure2
14.70
V(Min)
15.30
V(Max)
V OUT
Output Voltage
0.5A s I LOAD s 3A,
15
V
LM2576
18V s V IN s 40V
14.40/14.25
V(Min)
Circuit of Figure2
15.60/15.75
V(Max)
V OUT
Output Voltage
0.5A s I LOAD s 3A,
15
V
LM2576HV
18V s V IN s 60V
14.40/14.25
V(Min)
Circuit of Figure2
15.68/15.83
V(Max)
h
Efficiency
V IN e 18V, I LOAD e 3A
88
%
LM2576-ADJ, LM2576HV-ADJ
Electrical Characteristics Specifications with standard type face are for T J e 25 § C, and those with boldface
type apply over full Operating Temperature Range.
LM2576-ADJ
Symbol
Parameter
Conditions
LM2576HV-ADJ
Units
(Limits)
Limit
(Note 2)
Typ
SYSTEM PARAMETERS (Note 3) Test Circuit Figure2
V OUT
Feedback Voltage V IN e 12V, I LOAD e 0.5A
1.230
V
V OUT e 5V,
1.217
V(Min)
Circuit of Figure2
1.243
V(Max)
V OUT
Feedback Voltage
0.5A s I LOAD s 3A,
1.230
V
LM2576
8V s V IN s 40V
1.193/1.180 V(Min)
V OUT e 5V, Circuit of Figure2
1.267/1.280 V(Max)
V OUT
Feedback Voltage
0.5A s I LOAD s 3A,
1.230
V
LM2576HV
8V s V IN s 60V
1.193/1.180 V(Min)
V OUT e 5V, Circuit of Figure2
1.273/1.286 V(Max)
h
Efficiency
V IN e 12V, I LOAD e 3A, V OUT e 5V
77
%
3
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All Output Voltage Versions
Electrical Characteristics Specifications with standard type face are for T J e 25 § C, and those with boldface
type apply over full Operating Temperature Range. Unless otherwise specified, V IN e 12V for the 3.3V, 5V, and Adjustable
version, V IN e 25V for the 12V version, and V IN e 30V for the 15V version. I LOAD e 500 mA.
LM2576-XX
Symbol
Parameter
Conditions
LM2576HV-XX
Units
(Limits)
Limit
(Note 2)
Typ
DEVICE PARAMETERS
I b
Feedback Bias Current V OUT e 5V (Adjustable Version Only)
50
100/500
nA
f O
Oscillator Frequency
(Note 11)
52
kHz
47/42 kHz (Min)
58/63 kHz (Max)
V SAT
Saturation Voltage
I OUT e 3A (Note 4)
1.4
V
1.8/2.0
V(Max)
DC
Max Duty Cycle (ON)
(Note 5)
98
%
93
%(Min)
I CL
Current Limit
(Notes 4 and 11)
5.8
A
4.2/3.5
A(Min)
6.9/7.5
A(Max)
I L
Output Leakage Current
(Notes 6 and 7)
Output e 0V
2
mA(Max)
Output eb 1V 7.5
mA
Output eb 1V
30
mA(Max)
I Q
Quiescent Current
(Note 6)
5
mA
10
mA(Max)
I STBY
Standby Quiescent
ON/OFF Pin e 5V (OFF)
50
m A
Current
200
m A(Max)
i JA
Thermal Resistance
T Package, Junction to Ambient (Note 8)
65
i JA
T Package, Junction to Ambient (Note 9)
45
§ C/W
i JC
T Package, Junction to Case
2
i JA
S Package, Junction to Ambient (Note 10)
50
ON/OFF CON TRO L Test Circuit Figure2
V IH
ON/OFF Pin
V OUT e 0V
1.4
2.2/2.4
V(Min)
Logic Input Level
V OU T e Nominal Output Voltage 1.2 1.0/0.8 V(Max)
I IH ON/OFF Pin Input ON/OFF Pin e 5V (OFF) 12 m A
Current 30 m A(Max)
I IL ON/OFF Pin e 0V (ON) 0 m A
10 m A(Max)
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 do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%
production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods.
Note 3: External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the
LM2576/LM2576HV is used as shown in the Figure2 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics.
Note 4: Output pin sourcing current. No diode, inductor or capacitor connected to output.
Note 5: Feedback pin removed from output and connected to 0V.
Note 6: Feedback pin removed from output and connected to a 12V for the Adjustable, 3.3V, and 5V versions, and a 25V for the 12V and 15V versions, to force
the output transistor OFF.
Note 7: V IN e 40V (60V for high voltage version).
Note 8: Junction to ambient thermal resistance (no external heat sink) for the 5 lead TO-220 package mounted vertically, with
(/2
inch leads in a socket, or on a PC
board with minimum copper area.
Note 9: Junction to ambient thermal resistance (no external heat sink) for the 5 lead TO-220 package mounted vertically, with
(/4
inch leads soldered to a PC board
containing approximately 4 square inches of copper area surrounding the leads.
Note 10: If the TO-263 package is used, the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the package. Using
0.5 square inches of copper area, i JA is 50 § C/W, with 1 square inch of copper area, i JA is 37 § C/W, and with 1.6 or more square inches of copper area, i JA is
32 § C/W.
Note 11: The oscillator frequency reduces to approximately 11 kHz in the event of an output short or an overload which causes the regulated output voltage to drop
approximately 40% from the nominal output voltage. This self protection feature lowers the average power dissipation of the IC by lowering the minimum duty cycle
from 5% down to approximately 2%.
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V IL
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Typical Performance Characteristics (Circuit of Figure2)
Normalized Output Voltage
Line Regulation
Dropout Voltage
Standby
Current Limit
Quiescent Current
Quiescent Current
Switch Saturation
Oscillator Frequency
Voltage
Efficiency
Quiescent Current
Feedback Voltage
Minimum Operating Voltage
vs Duty Cycle
vs Duty Cycle
TL/H/11476±3
5
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