LM2576
3.0 A, 15 V, Step−Down
Switching Regulator
The LM2576 series of regulators are monolithic integrated circuits
ideally suited for easy and convenient design of a step−down
switching regulator (buck converter). All circuits of this series are
capable of driving a 3.0 A load with excellent line and load regulation.
These devices are available in fixed output voltages of 3.3 V, 5.0 V,
12 V, 15 V, and an adjustable output version.
These regulators were designed to minimize the number of external
components to simplify the power supply design. Standard series of
inductors optimized for use with the LM2576 are offered by several
different inductor manufacturers.
Since the LM2576 converter is a switch−mode power supply, its
efficiency is significantly higher in comparison with popular
three−terminal linear regulators, especially with higher input voltages.
In many cases, the power dissipated is so low that no heatsink is
required or its size could be reduced dramatically.
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.
The LM2576 features include a guaranteed
±4%
tolerance on output
voltage within specified input voltages and output load conditions, and
±10%
on the oscillator frequency (±2% over 0°C to 125°C). External
shutdown is included, featuring 80
mA
(typical) standby current. The
output switch includes cycle−by−cycle current limiting, as well as
thermal shutdown for full protection under fault conditions.
Features
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5
TO−220
TV SUFFIX
CASE 314B
Heatsink surface connected to Pin 3
1
5
Pin
1.
2.
3.
4.
5.
TO−220
T SUFFIX
CASE 314D
•
3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions
•
Adjustable Version Output Voltage Range, 1.23 to 37 V
±4%
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Maximum Over Line and Load Conditions
Guaranteed 3.0 A Output Current
Wide Input Voltage Range
Requires Only 4 External Components
52 kHz Fixed Frequency Internal Oscillator
TTL Shutdown Capability, Low Power Standby Mode
High Efficiency
Uses Readily Available Standard Inductors
Thermal Shutdown and Current Limit Protection
Moisture Sensitivity Level (MSL) Equals 1
Pb−Free Packages are Available
V
in
Output
Ground
Feedback
ON/OFF
1
5
D
2
PAK
D2T SUFFIX
CASE 936A
Heatsink surface (shown as terminal 6 in
case outline drawing) is connected to Pin 3
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 24 of this data sheet.
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 25 of this data sheet.
Applications
Simple High−Efficiency Step−Down (Buck) Regulator
Efficient Pre−Regulator for Linear Regulators
On−Card Switching Regulators
Positive to Negative Converter (Buck−Boost)
Negative Step−Up Converters
Power Supply for Battery Chargers
1
Publication Order Number:
LM2576/D
©
Semiconductor Components Industries, LLC, 2006
January, 2006 − Rev. 8
LM2576
Typical Application
(Fixed Output Voltage Versions)
Feedback
7.0 V − 40 V
Unregulated
DC Input
+V
in
C
in
100
mF
1
3
GN
D
5
LM2576
4
Output
2
ON/OFF
L1
100
mH
D1
1N5822
C
out
1000
mF
5.0 V Regulated
Output 3.0 A Load
Representative Block Diagram and Typical Application
+V
in
1
C
in
4
Feedback
R2
Fixed Gain
Error Amplifier Comparator
Current
Limit
Unregulated
DC Input
3.1 V Internal
Regulator
ON/OFF
ON/OFF
5
Output
Voltage Versions
3.3 V
5.0 V
12 V
15 V
For adjustable version
R1 = open, R2 = 0
W
R2
(W)
1.7 k
3.1 k
8.84 k
11.3 k
R1
1.0 k
Driver
Freq
Shift
18 kHz
52 kHz
Oscillator
Latch
Output
1.0 Amp
Switch
Reset
Thermal
Shutdown
2
GND
3
D1
L1
Regulated
Output
V
out
C
out
Load
1.235 V
Band−Gap
Reference
This device contains 162 active transistors.
Figure 1. Block Diagram and Typical Application
MAXIMUM RATINGS
Rating
Maximum Supply Voltage
ON/OFF Pin Input Voltage
Output Voltage to Ground (Steady−State)
Power Dissipation
Case 314B and 314D (TO−220, 5−Lead)
Thermal Resistance, Junction−to−Ambient
Thermal Resistance, Junction−to−Case
Case 936A (D
2
PAK)
Thermal Resistance, Junction−to−Ambient
Thermal Resistance, Junction−to−Case
Storage Temperature Range
Minimum ESD Rating (Human Body Model: C = 100 pF, R = 1.5 kW)
Lead Temperature (Soldering, 10 seconds)
Maximum Junction Temperature
Symbol
V
in
−
−
P
D
R
qJA
R
qJC
P
D
R
qJA
R
qJC
T
stg
−
−
T
J
Value
45
−0.3 V
≤
V
≤
+V
in
−1.0
Internally Limited
65
5.0
Internally Limited
70
5.0
−65 to +150
2.0
260
150
Unit
V
V
V
W
°C/W
°C/W
W
°C/W
°C/W
°C
kV
°C
°C
Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit
values (not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied,
damage may occur and reliability may be affected.
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LM2576
OPERATING RATINGS
(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.)
Rating
Operating Junction Temperature Range
Supply Voltage
Symbol
T
J
V
in
Value
−40 to +125
40
Unit
°C
V
SYSTEM PARAMETERS
(Note 1 Test Circuit Figure 15)
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, V
in
= 12 V for the 3.3 V, 5.0 V, and Adjustable version, V
in
= 25 V
for the 12 V version, and V
in
= 30 V for the 15 V version. I
Load
= 500 mA. For typical values T
J
= 25°C, for min/max values T
J
is the
operating junction temperature range that applies Note 2, unless otherwise noted.)
Characteristics
LM2576−3.3
(Note 1 Test Circuit Figure 15)
Output Voltage (V
in
= 12 V, I
Load
= 0.5 A, T
J
= 25°C)
Output Voltage (6.0 V
≤
V
in
≤
40 V, 0.5 A
≤
I
Load
≤
3.0 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 12 V, I
Load
= 3.0 A)
LM2576−5
(Note 1 Test Circuit Figure 15)
Output Voltage (V
in
= 12 V, I
Load
= 0.5 A, T
J
= 25°C)
Output Voltage (8.0 V
≤
V
in
≤
40 V, 0.5 A
≤
I
Load
≤
3.0 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 12 V, I
Load
= 3.0 A)
LM2576−12
(Note 1 Test Circuit Figure 15)
Output Voltage (V
in
= 25 V, I
Load
= 0.5 A, T
J
= 25°C)
Output Voltage (15 V
≤
V
in
≤
40 V, 0.5 A
≤
I
Load
≤
3.0 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 15 V, I
Load
= 3.0 A)
LM2576−15
(Note 1 Test Circuit Figure 15)
Output Voltage (V
in
= 30 V, I
Load
= 0.5 A, T
J
= 25°C)
Output Voltage (18 V
≤
V
in
≤
40 V, 0.5 A
≤
I
Load
≤
3.0 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 18 V, I
Load
= 3.0 A)
LM2576 ADJUSTABLE VERSION
(Note 1 Test Circuit Figure 15)
Feedback Voltage (V
in
= 12 V, I
Load
= 0.5 A, V
out
= 5.0 V, T
J
= 25°C)
Feedback Voltage (8.0 V
≤
V
in
≤
40 V, 0.5 A
≤
I
Load
≤
3.0 A, V
out
= 5.0 V)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 12 V, I
Load
= 3.0 A, V
out
= 5.0 V)
V
out
V
out
1.193
1.18
η
−
1.23
−
77
1.267
1.28
−
%
1.217
1.23
1.243
V
V
V
out
V
out
14.4
14.25
η
−
15
−
88
15.6
15.75
−
%
14.7
15
15.3
V
V
V
out
V
out
11.52
11.4
η
−
12
−
88
12.48
12.6
−
%
11.76
12
12.24
V
V
V
out
V
out
4.8
4.75
η
−
5.0
−
77
5.2
5.25
−
%
4.9
5.0
5.1
V
V
V
out
V
out
3.168
3.135
η
−
3.3
−
75
3.432
3.465
−
%
3.234
3.3
3.366
V
V
Symbol
Min
Typ
Max
Unit
1. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance.
When the LM2576 is used as shown in the Figure 15 test circuit, system performance will be as shown in system parameters section.
2. Tested junction temperature range for the LM2576:
T
low
= −40°C
T
high
= +125°C
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LM2576
DEVICE PARAMETERS
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, V
in
= 12 V for the 3.3 V, 5.0 V, and Adjustable version, V
in
= 25 V
for the 12 V version, and V
in
= 30 V for the 15 V version. I
Load
= 500 mA. For typical values T
J
= 25°C, for min/max values T
J
is the
operating junction temperature range that applies [Note 2], unless otherwise noted.)
Characteristics
ALL OUTPUT VOLTAGE VERSIONS
Feedback Bias Current (V
out
= 5.0 V Adjustable Version Only)
T
J
= 25°C
T
J
= −40 to +125°C
Oscillator Frequency Note 3
T
J
= 25°C
T
J
= 0 to +125°C
T
J
= −40 to +125°C
Saturation Voltage (I
out
= 3.0 A Note 4)
T
J
= 25°C
T
J
= −40 to +125°C
Max Duty Cycle (“on”) Note 5
Current Limit (Peak Current Notes 3 and 4)
T
J
= 25°C
T
J
= −40 to +125°C
Output Leakage Current Notes 6 and 7, T
J
= 25°C
Output = 0 V
Output = −1.0 V
Quiescent Current Note 6
T
J
= 25°C
T
J
= −40 to +125°C
Standby Quiescent Current (ON/OFF Pin = 5.0 V (“off”))
T
J
= 25°C
T
J
= −40 to +125°C
ON/OFF Pin Logic Input Level (Test Circuit Figure 15)
V
out
= 0 V
T
J
= 25°C
T
J
= −40 to +125°C
V
out
= Nominal Output Voltage
T
J
= 25°C
T
J
= −40 to +125°C
ON/OFF Pin Input Current (Test Circuit Figure 15)
ON/OFF Pin = 5.0 V (“off”), T
J
= 25°C
ON/OFF Pin = 0 V (“on”), T
J
= 25°C
I
b
−
−
f
osc
−
47
42
V
sat
−
−
DC
I
CL
4.2
3.5
I
L
−
−
I
Q
−
−
I
stby
−
−
V
IH
2.2
2.4
V
IL
−
−
I
IH
I
IL
−
−
1.2
−
15
0
1.0
0.8
mA
30
5.0
1.4
−
−
−
80
−
200
400
V
5.0
−
9.0
11
mA
0.8
6.0
2.0
20
mA
5.8
−
6.9
7.5
mA
94
1.5
−
98
1.8
2.0
−
%
A
52
−
−
−
58
63
V
25
−
100
200
kHz
nA
Symbol
Min
Typ
Max
Unit
3. The oscillator frequency reduces to approximately 18 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 dissipation of the IC by
lowering the minimum duty cycle from 5% down to approximately 2%.
4. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to output pin.
5. Feedback (Pin 4) removed from output and connected to 0 V.
6. Feedback (Pin 4) removed from output and connected to +12 V for the Adjustable, 3.3 V, and 5.0 V versions, and +25 V for the 12 V and
15 V versions, to force the output transistor “off”.
7. V
in
= 40 V.
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LM2576
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 15)
1.0
Vout , OUTPUT VOLTAGE CHANGE (%)
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
−50
V
in
= 20 V
I
Load
= 500 mA
Normalized at T
J
= 25°C
Vout , OUTPUT VOLTAGE CHANGE (%)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
0
5.0
10
15
20
25
30
35
40
12 V and 15 V
3.3 V, 5.0 V and ADJ
I
Load
= 500 mA
T
J
= 25°C
−25
0
25
50
75
100
125
T
J
, JUNCTION TEMPERATURE (°C)
V
in
, INPUT VOLTAGE (V)
Figure 2. Normalized Output Voltage
Figure 3. Line Regulation
2.0
INPUT − OUTPUT DIFFERENTIAL (V)
I O, OUTPUT CURRENT (A)
I
Load
= 3.0 A
1.5
6.5
V
in
= 25 V
6.0
5.5
5.0
4.5
4.0
−50
1.0
I
Load
= 500 mA
0.5
L1 = 150
mH
R
ind
= 0.1
W
0
−50
−25
0
25
50
75
100
125
−25
0
25
50
75
100
125
T
J
, JUNCTION TEMPERATURE (°C)
T
J
, JUNCTION TEMPERATURE (°C)
Figure 4. Dropout Voltage
Figure 5. Current Limit
20
I Q, QUIESCENT CURRENT (mA)
18
16
14
12
10
8.0
6.0
4.0
0
5.0
10
15
20
25
30
35
40
I
Load
= 200 mA
I
Load
= 3.0 A
V
out
= 5.0 V
Measured at
Ground Pin
T
J
= 25°C
I stby , STANDBY QUIESCENT CURRENT (
μA)
200
180
160
140
120
100
80
60
40
20
0
−50
V
in
= 12 V
V
in
= 40 V
V
ON/OFF
= 5.0 V
−25
0
25
50
75
100
125
V
in
, INPUT VOLTAGE (V)
T
J
, JUNCTION TEMPERATURE (°C)
Figure 6. Quiescent Current
Figure 7. Standby Quiescent Current
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