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FEATURES
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
NC
NC
OUTPUT
NC
GND
NC
FB
NC
V
IN
NC
GND
GND
GND
GND
NC
ON/OFF
N (PDIP) PACKAGE
(TOP VIEW)
KTT (TO-263) PACKAGE
(TOP VIEW)
1
2
3
4
5
GND
ON/OFF
FEEDBACK
GND
OUTPUT
V
IN
APPLICATIONS
DESCRIPTION/ORDERING INFORMATION
LM2575
1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
Fixed 3.3-V, 5-V, 12-V, and 15-V Options With
5% Regulation (Max) Over Line, Load, and
Temperature Conditions
Adjustable Option With a Range of 1.23 V to
37 V and
4% Regulation (Max) Over Line,
Load, and Temperature Conditions
Specified 1-A Output Current
Wide Input Voltage Range
...
4.75 V to 40 V
Requires Only Four External Components
(Fixed Versions) and Uses Readily Available
Standard Inductors
52-kHz (Typ) Fixed-Frequency Internal
Oscillator
TTL Shutdown Capability With 50-
A (Typ)
Standby Current
High Efficiency
...
as High as 88% (Typ)
Thermal Shutdown and Current-Limit
Protection With Cycle-by-Cycle Current
Limiting
Simple High-Efficiency Step-Down (Buck)
Regulator
Pre-Regulator for Linear Regulators
On-Card Switching Regulators
Positive-to-Negative Converter (Buck-Boost)
The LM2575 greatly simplifies the design of switching power supplies by conveniently providing all the active
functions needed for a step-down (buck) switching regulator in an integrated circuit. Accepting a wide input
voltage range and available in fixed output voltages of 3.3 V, 5 V, 12 V, 15 V, or an adjustable output version,
the LM2575 has an integrated switch capable of delivering 1 A of load current, with excellent line and load
regulation. The device also offers internal frequency compensation, a fixed-frequency oscillator, cycle-by-cycle
current limiting, and thermal shutdown. In addition, a manual shutdown is available via an external ON/OFF pin.
The LM2575 represents a superior alternative to popular three-terminal linear regulators. Due to its high
efficiency, it significantly reduces the size of the heat sink and, in many cases, no heat sink is required.
Optimized for use with standard series of inductors available from several different manufacturers, the LM2575
greatly simplifies the design of switch-mode power supplies by requiring a minimal addition of only four to six
external components for operation.
The LM2575 is characterized for operation over the virtual junction temperature range of 40
C to 125
C.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Copyright 2005, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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LM2575
1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
ORDERING INFORMATION
V
O
T
J
PACKAGE
(1)
ORDERABLE PART NUMBER
TOP-SIDE MARKING
(NOM)
3.3 V
LM2575-33IN
PREVIEW
5 V
LM2575-05IN
PREVIEW
12 V
PDIP N
Tube of 25
LM2575-12IN
PREVIEW
15 V
LM2575-15IN
PREVIEW
ADJ
LM2575IN
LM2575IN
Tube of 50
LM2575-33IKTT
3.3 V
PREVIEW
Reel of 2000
LM2575-33IKTTR
40
C to 125
C
Tube of 50
LM2575-05IKTT
5 V
PREVIEW
Reel of 2000
LM2575-05IKTTR
Tube of 50
LM2575-12IKTT
12 V
TO-263 KTT
PREVIEW
Reel of 2000
LM2575-12IKTTR
Tube of 50
LM2575-15IKTT
15 V
PREVIEW
Reel of 2000
LM2575-15IKTTR
Tube of 50
LM2575IKTT
ADJ
PREVIEW
Reel of 2000
LM2575IKTTR
(1)
Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are available at
www.ti.com/sc/package.
2
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Internal
Regulator
On/Off
_
+
_
+
1.23-V
Band-Gap
Reference
52-kHz
Oscillator
Reset
Thermal
Shutdown
Current
Limit
FEEDBACK
4
C
IN
+
V
IN
1
Unregulated
DC Input
GND
3
OUTPUT
2
ON/OFF
5
C
OUT
+
D1
L
O
A
D
V
OUT
1-A
Switch
Driver
Fixed-Gain
Error Amp
Comparator
R2
R1
1 k
W
3.3 V: R2 = 1.7 k
W
5 V: R2 = 3.1 k
W
12 V: R2 = 8.84 k
W
15 V: R2 = 11.3 k
W
ADJ: R1 = Open, R2 = 0
L1
LM2575-05
7-V to 40-V
Unregulated
DC Input
C
IN
100
F
+
+V
IN
1
3
GND
5
ON/OFF
D1
1N5819
OUTPUT
2
L1
330
H
C
OUT
330
F
+
FEEDBACK
4
5-V
Regulated
Output
1-A Load
L2
20
H
C1
100
F
+
Optional Output Ripple Filter
LM2575
1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
FUNCTIONAL BLOCK DIAGRAM
A.
Pin numbers are for the KTT (TO-263) package.
A.
Pin numbers are for the KTT (TO-263) package.
Figure 1. Typical Application Circuit (Fixed Version)
3
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Absolute Maximum Ratings
(1)
Package Thermal Data
(1)
Recommended Operating Conditions
LM2575
1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
V
IN
Supply voltage
42
V
ON/OFF pin input voltage
0.3
V
IN
V
Output voltage to GND (steady state)
1
V
T
J
Maximum junction temperature
150
C
T
stg
Storage temperature range
65
150
C
(1)
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating
conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
PACKAGE
BOARD
JC
JCB
JA
PDIP (N)
High K, JESD 51-7
51
C/W
67
C/W
TO-263 (KTT)
High K, JESD 51-5
TBD
TBD
(1)
Maximum power dissipation is a function of T
J
(max),
JA
, and T
A
. The maximum allowable power dissipation at any allowable ambient
temperature is P
D
= (T
J
(max) T
A
)/
JA
. Operating at the absolute maximum T
J
of 150
C can affect reliability.
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
V
IN
Supply voltage
4.75
40
V
T
J
Operating virtual junction temperature
40
125
C
4
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Electrical Characteristics
LM2575
1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D JANUARY 2005 REVISED JULY 2005
I
LOAD
= 200 mA, V
IN
= 12 V for 3.3-V, 5-V, and adjustable versions, V
IN
= 25 V for 12-V version, V
IN
= 30 V for 15-V version
(unless otherwise noted) (see
Figure 2
)
PARAMETER
TEST CONDITIONS
T
J
MIN
TYP
MAX
UNIT
V
IN
= 12 V, I
LOAD
= 0.2 A
25
C
3.234
3.3
3.366
LM2575-33
25
C
3.168
3.3
3.432
4.75 V
V
IN
40 V,
0.2 A
I
LOAD
1 A
Full range
3.135
3.465
V
IN
= 12 V, I
LOAD
= 0.2 A
25
C
4.9
5
5.1
LM2575-05
25
C
4.8
5
5.2
8 V
V
IN
40 V,
0.2 A
I
LOAD
1 A
Full range
4.75
5.25
V
OUT
Output voltage
V
V
IN
= 25 V, I
LOAD
= 0.2 A
25
C
11.76
12
12.24
LM2575-12
25
C
11.52
12
12.48
15 V
V
IN
40 V,
0.2 A
I
LOAD
1 A
Full range
11.4
12.6
V
IN
= 30 V, I
LOAD
= 0.2 A
25
C
14.7
15
15.3
LM2575-15
25
C
14.4
15
15.6
18 V
V
IN
40 V,
0.2 A
I
LOAD
1 A
Full range
14.25
15
15.75
V
IN
= 12 V, V
OUT
= 5 V,
25
C
1.217
1.23
1.243
I
LOAD
= 0.2 A
Feedback voltage
LM2575-ADJ
V
25
C
1.193
1.23
1.267
8 V
V
IN
40 V, V
OUT
= 5 V,
0.2 A
I
LOAD
1 A
Full range
1.18
1.28
LM2575-33
V
IN
= 12 V, I
LOAD
= 1 A
75
LM2575-05
V
IN
= 12 V, I
LOAD
= 1 A
77
LM2575-12
V
IN
= 15 V, I
LOAD
= 1 A
88
Efficiency
25
C
%
LM2575-15
V
IN
= 18 V, I
LOAD
= 1 A
88
V
IN
= 12 V, V
OUT
= 5 V,
LM2575-ADJ
77
I
LOAD
= 1 A
25
C
50
100
I
IB
Feedback bias current
V
OUT
= 5 V (ADJ version only)
nA
Full range
500
25
C
47
52
58
f
o
Oscillator frequency
(1)
kHz
Full range
42
63
25
C
0.9
1.2
V
SAT
Saturation voltage
I
OUT
= 1 A
(2)
V
Full range
1.4
Maximum duty cycle
(3)
25
C
93
98
%
25
C
1.7
2.8
3.6
I
CL
Peak current
(1) (2)
A
Full range
1.3
4
V
IN
= 40
(4)
, Output = 0 V
2
I
L
Output leakage current
25
C
mA
V
IN
= 40
(4)
, Output = 1 V
7.5
30
I
Q
Quiescent current
(4)
25
C
5
10
mA
I
STBY
Standby quiescent current
OFF (ON/OFF pin = 5 V)
25
C
50
200
A
25
C
2.2
1.4
V
IH
OFF (V
OUT
= 0 V)
Full range
2.4
ON/OFF logic input level
V
25
C
1.2
1
V
IL
ON (V
OUT
= nominal voltage)
Full range
0.8
I
IH
OFF (ON/OFF pin = 5 V)
12
30
ON/OFF input current
25
C
A
I
IL
OFF (ON/OFF pin = 0 V)
0
10
(1)
In the event of an output short or an overload condition, self-protection features lower the oscillator frequency to
18 kHz and the
minimum duty cycle from 5% to
2%. The resulting output voltage drops to
40% of its nominal value, causing the average power
dissipated by the IC to lower.
(2)
Output is not connected to diode, inductor, or capacitor. Output is sourcing current.
(3)
Feedback is disconnected from output and connected to 0 V.
(4)
To force the output transistor off, FEEDBACK is disconnected from output and connected to 12 V for the adjustable, 3.3-V, and 5-V
versions; and 25 V for the 12-V and 15-V versions.
5
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