Semiconductor Components Industries, LLC, 2004
May, 2004 - Rev. 6
1
Publication Order Number:
LM2575/D
LM2575
1.0 A, Adjustable Output
Voltage, Step-Down
Switching Regulator
The LM2575 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 1.0 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 LM2575 are offered by several
different inductor manufacturers.
Since the LM2575 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 by the LM2575 regulator is so
low, that no heatsink is required or its size could be reduced
dramatically.
The LM2575 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
3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions
Adjustable Version Output Voltage Range of 1.23 V to 37 V
4%
Maximum Over Line and Load Conditions
Guaranteed 1.0 A Output Current
Wide Input Voltage Range: 4.75 V to 40 V
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
Applications
Simple and High-Efficiency Step-Down (Buck) Regulators
Efficient Pre-Regulator for Linear Regulators
On-Card Switching Regulators
Positive to Negative Converters (Buck-Boost)
Negative Step-Up Converters
Power Supply for Battery Chargers
See detailed ordering and shipping information in the package
dimensions section on page 24 of this data sheet.
ORDERING INFORMATION
1
5
TO-220
TV SUFFIX
CASE 314B
1
5
1
5
Heatsink surface connected to Pin 3
TO-220
T SUFFIX
CASE 314D
Pin
1.
V
in
2.
Output
3.
Ground
4.
Feedback
5.
ON/OFF
D
2
PAK
D2T SUFFIX
CASE 936A
Heatsink surface (shown as terminal 6 in
case outline drawing) is connected to Pin 3
See general marking information in the device marking
section on page 24 of this data sheet.
DEVICE MARKING INFORMATION
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*For additional information on our Pb-Free strategy
and soldering details, please download the
ON Semiconductor Soldering and Mounting
Techniques Reference Manual, SOLDERRM/D.
LM2575
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2
Figure 1. Block Diagram and Typical Application
7.0 V - 40 V
Unregulated
DC Input
L1
330
mH
GND
+V
in
1
C
in
100
mF
3
ON/OFF
5
Output
2
Feedback
4
D1
1N5819
C
out
330
mF
Typical Application (Fixed Output Voltage Versions)
Representative Block Diagram and Typical Application
Unregulated
DC Input
+V
in
1
C
out
Feedback
4
C
in
L1
D1
R2
R1
1.0 k
Output
2
GND
3
ON/OFF
5
Reset
Latch
Thermal
Shutdown
52 kHz
Oscillator
1.235 V
Band-Gap
Reference
Freq
Shift
18 kHz
Comparator
Fixed Gain
Error Amplifier
Current
Limit
Driver
1.0 Amp
Switch
ON/OFF
3.1 V Internal
Regulator
Regulated
Output
V
out
Load
Output
Voltage Versions
3.3 V
5.0 V
12 V
15 V
R2
(
W)
1.7 k
3.1 k
8.84 k
11.3 k
For adjustable version
R1 = open, R2 = 0
W
LM2575
5.0 V Regulated
Output 1.0 A Load
This device contains 162 active transistors.
ABSOLUTE MAXIMUM RATINGS
(Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.)
Rating
Symbol
Value
Unit
Maximum Supply Voltage
V
in
45
V
ON/OFF Pin Input Voltage
-
-0.3 V
V
+V
in
V
Output Voltage to Ground (Steady-State)
-
-1.0
V
Power Dissipation
Case 314B and 314D (TO-220, 5-Lead)
P
D
Internally Limited
W
Thermal Resistance, Junction-to-Ambient
R
q
JA
65
C/W
Thermal Resistance, Junction-to-Case
R
q
JC
5.0
C/W
Case 936A (D
2
PAK)
P
D
Internally Limited
W
Thermal Resistance, Junction-to-Ambient (Figure 34)
R
q
JA
70
C/W
Thermal Resistance, Junction-to-Case
R
q
JC
5.0
C/W
Storage Temperature Range
T
stg
-65 to +150
C
Minimum ESD Rating (Human Body Model: C = 100 pF, R = 1.5 k
W
)
-
3.0
kV
Lead Temperature (Soldering, 10 s)
-
260
C
Maximum Junction Temperature
T
J
150
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.
LM2575
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3
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
Symbol
Value
Unit
Operating Junction Temperature Range
T
J
-40 to +125
C
Supply Voltage
V
in
40
V
SYSTEM PARAMETERS
([Note 1] Test Circuit Figure 14)
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
= 200 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
Symbol
Min
Typ
Max
Unit
LM2575-3.3
(Note 1 Test Circuit Figure 14)
Output Voltage (V
in
= 12 V, I
Load
= 0.2 A, T
J
= 25
C)
V
out
3.234
3.3
3.366
V
Output Voltage (4.75 V
V
in
40 V, 0.2 A
I
Load
1.0 A)
V
out
V
T
J
= 25
C
3.168
3.3
3.432
T
J
= -40 to +125
C
3.135
-
3.465
Efficiency (V
in
= 12 V, I
Load
= 1.0 A)
-
75
-
%
LM2575-5
([Note 1] Test Circuit Figure 14)
Output Voltage (V
in
= 12 V, I
Load
= 0.2 A, T
J
= 25
C)
V
out
4.9
5.0
5.1
V
Output Voltage (8.0 V
V
in
40 V, 0.2 A
I
Load
1.0 A)
V
out
V
T
J
= 25
C
4.8
5.0
5.2
T
J
= -40 to +125
C
4.75
-
5.25
Efficiency (V
in
= 12 V, I
Load
= 1.0 A)
-
77
-
%
LM2575-12
(Note 1 Test Circuit Figure 14)
Output Voltage (V
in
= 25 V, I
Load
= 0.2 A, T
J
= 25
C)
V
out
11.76
12
12.24
V
Output Voltage (15 V
V
in
40 V, 0.2 A
I
Load
1.0 A)
V
out
V
T
J
= 25
C
11.52
12
12.48
T
J
= -40 to +125
C
11.4
-
12.6
Efficiency (V
in
= 15V, I
Load
= 1.0 A)
-
88
-
%
LM2575-15
(Note 1 Test Circuit Figure 14)
Output Voltage (V
in
= 30 V, I
Load
= 0.2 A, T
J
= 25
C)
V
out
14.7
15
15.3
V
Output Voltage (18 V
V
in
40 V, 0.2 A
I
Load
1.0 A)
V
out
V
T
J
= 25
C
14.4
15
15.6
T
J
= -40 to +125
C
14.25
-
15.75
Efficiency (V
in
= 18 V, I
Load
= 1.0 A)
-
88
-
%
LM2575 ADJUSTABLE VERSION
(Note 1 Test Circuit Figure 14)
Feedback Voltage (V
in
= 12 V, I
Load
= 0.2 A, V
out
= 5.0 V, T
J
= 25
C)
V
FB
1.217
1.23
1.243
V
Feedback Voltage (8.0 V
V
in
40 V, 0.2 A
I
Load
1.0 A, V
out
= 5.0 V)
V
FB
V
T
J
= 25
C
1.193
1.23
1.267
T
J
= -40 to +125
C
1.18
-
1.28
Efficiency (V
in
= 12 V, I
Load
= 1.0 A, V
out
= 5.0 V)
-
77
-
%
1. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance.
When the LM2575 is used as shown in the
Figure 14 test circuit, system performance will be as shown in system parameters section.
2. Tested junction temperature range for the LM2575: T
low
= -40
C T
high
= +125
C
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4
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
= 200 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
Symbol
Min
Typ
Max
Unit
ALL OUTPUT VOLTAGE VERSIONS
Feedback Bias Current (V
out
= 5.0 V Adjustable Version Only)
I
b
nA
T
J
= 25
C
-
25
100
T
J
= -40 to +125
C
-
-
200
Oscillator Frequency Note 3
f
osc
kHz
T
J
= 25
C
-
52
-
T
J
= 0 to +125
C
47
-
58
T
J
= -40 to +125
C
42
-
63
Saturation Voltage (I
out
= 1.0 A Note 4)
V
sat
V
T
J
= 25
C
-
1.0
1.2
T
J
= -40 to +125
C
-
-
1.3
Max Duty Cycle ("on") Note 5
DC
94
98
-
%
Current Limit (Peak Current Notes 4 and 3)
I
CL
A
T
J
= 25
C
1.7
2.3
3.0
T
J
= -40 to +125
C
1.4
-
3.2
Output Leakage Current Notes 6 and 7, T
J
= 25
C
I
L
mA
Output = 0 V
-
0.8
2.0
Output = -1.0 V
-
6.0
20
Quiescent Current Note 6
I
Q
mA
T
J
= 25
C
-
5.0
9.0
T
J
= -40 to +125
C
-
-
11
Standby Quiescent Current (ON/OFF Pin = 5.0 V ("off"))
I
stby
m
A
T
J
= 25
C
-
80
200
T
J
= -40 to +125
C
-
-
400
ON/OFF Pin Logic Input Level (Test Circuit Figure 14)
V
V
out
= 0 V
V
IH
T
J
= 25
C
2.2
1.4
-
T
J
= -40 to +125
C
2.4
-
-
V
out
= Nominal Output Voltage
V
IL
T
J
= 25
C
-
1.2
1.0
T
J
= -40 to +125
C
-
-
0.8
ON/OFF Pin Input Current (Test Circuit Figure 14)
m
A
ON/OFF Pin = 5.0 V ("off"), T
J
= 25
C
I
IH
-
15
30
ON/OFF Pin = 0 V ("on"), T
J
= 25
C
I
IL
-
0
5.0
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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5
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 14)
V out
, OUTPUT
VOL
T
AGE CHANGE (%)
0
20
-50
3.0
0
-50
2.0
0
1.2
-50
I Q
, QUIESCENT
CURRENT
(mA)
V
in
, INPUT VOLTAGE (V)
I O
, OUTPUT
CURRENT
(A)
T
J
, JUNCTION TEMPERATURE (
C)
V
in
, INPUT VOLTAGE (V)
INPUT-OUTPUT
DIFFERENTIAL
(V)
T
J
, JUNCTION TEMPERATURE (
C)
V
sat
, SA
TURA
TION VOL
T
AGE (V)
SWITCH CURRENT (A)
V out
, OUTPUT
VOL
T
AGE CHANGE (%)
Figure 2. Normalized Output Voltage
T
J
, JUNCTION TEMPERATURE (
C)
Figure 3. Line Regulation
V
in
= 20 V
I
Load
= 200 mA
Normalized at
T
J
= 25
C
Figure 4. Switch Saturation Voltage
Figure 5. Current Limit
Figure 6. Dropout Voltage
Figure 7. Quiescent Current
I
Load
= 200 mA
T
J
= 25
C
3.3 V, 5.0 V and Adj
12 V and 15 V
25
C
V
in
= 25 V
V
out
= 5.0 V
Measured at
Ground Pin
T
J
= 25
C
I
Load
= 200 mA
I
Load
= 1.0 A
DV
out
= 5%
R
ind
= 0.2
W
125
C
-40
C
5.0
-25
10
0
20
15
25
25
75
50
35
30
40
100
125
0.8
0.4
0.4
0
0
-0.2
-0.4
0.6
0.2
1.0
0.6
0.2
-0.2
-0.6
2.5
1.5
0.5
0
2.0
1.0
14
10
6.0
4.0
18
12
8.0
16
1.1
0.9
0.7
0.5
1.0
0.8
0.6
1.2
0.8
0.4
1.0
0.6
1.8
1.4
1.6
0.4
-25
0.1
0
0.2
25
0.3
50
0.4
75
0.5
100
0.6
125
0.7
5.0
-25
10
0
15
25
20
50
25
75
30
100
35
125
0.8
0.9
1.0
40
I
Load
= 200 mA
I
Load
= 1.0 A
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