LM2574, NCV2574
0.5 A, Adjustable Output
Voltage, Step−Down
Switching Regulator
The LM2574 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 0.5 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 LM2574 are offered by several
different inductor manufacturers.
Since the LM2574 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 most cases, the power dissipated by the LM2574 regulator is so low,
that the copper traces on the printed circuit board are normally the only
heatsink needed and no additional heatsinking is required.
The LM2574 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 60
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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16
1
SO−16 WB
DW SUFFIX
CASE 751G
8
1
PDIP−8
N SUFFIX
CASE 626
PIN CONNECTIONS
•
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%
max
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
over Line and Load Conditions
Guaranteed 0.5 A Output Current
Wide Input Voltage Range: 4.75 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
NCV Prefix for Automotive and Other Applications Requiring Site
and Control Changes
Pb−Free Packages are Available*
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
*
*
FB
Sig Gnd
ON/OFF
Pwr Gnd
*
*
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
*
*
Output
*
V
in
*
*
*
(Top View)
FB
Sig Gnd
ON/OFF
Pwr Gnd
1
2
3
4
8
7
6
5
*
Output
*
V
in
(Top View)
* No internal connection, but should be soldered to
*
PC board for best heat transfer.
Applications
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 24 of this data sheet.
*For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting
Techniques Reference Manual, SOLDERRM/D.
©
Semiconductor Components Industries, LLC, 2006
1
August, 2006 − Rev. 8
Publication Order Number:
LM2574/D
LM2574, NCV2574
Typical Application
(Fixed Output Voltage Versions)
Feedback
7.0 − 40 V
Unregulated
DC Input
+V
in
C
in
22
mF
5
(12)
2
(4)
Sig
Gnd
4
(6)
Pwr 3
Gnd
(5)
(3)
LM2574
(14)
1
Output
7
ON/OFF
L1
330
mH
D1
1N5819
C
out
220
mF
5.0 V Regulated
Output 0.5 A Load
Representative Block Diagram and Typical Application
+V
in
5
C
in
1
Feedback
R2
Fixed Gain
Error Amplifier Comparator
(3)
Current
Limit
(12)
Unregulated
DC Input
3.1 V Internal
Regulator
ON/OFF
ON/OFF
3
(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
Sig Gnd
2
(4)
Driver
Freq
Shift
18 kHz
52 kHz
Oscillator
Latch
Output
1.0 Amp
Switch
Reset
Thermal
Shutdown
7 (14)
Pwr Gnd
4
(6)
D1
L1
V
out
C
out
Load
1.235 V
Band−Gap
Reference
NOTE: Pin numbers in ( ) are for the SO−16W package.
Figure 1. Block Diagram and Typical Application
ABSOLUTE MAXIMUM RATINGS
(Absolute Maximum Ratings indicate limits beyond which damage to the device may occur).
Rating
Maximum Supply Voltage
ON/OFF Pin Input Voltage
Output Voltage to Ground (Steady State)
DW Suffix, Plastic Package Case 751G
Max Power Dissipation
Thermal Resistance, Junction−to−Air
N Suffix, Plastic Package Case 626
Max Power Dissipation
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
−
T
J
260
150
°C
°C
Symbol
V
in
−
−
P
D
R
qJA
P
D
R
qJA
R
qJC
T
stg
−
Value
45
−0.3 V
≤
V
≤
+V
in
−1.0
Internally Limited
145
Internally Limited
100
5.0
−65°C to +150°C
2.0
Unit
V
V
V
W
°C/W
W
°C/W
°C/W
°C
kV
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.
NOTE: ESD data available upon request.
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2
LM2574, NCV2574
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 16)
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, V
in
= 30 V for the 15 V version. I
Load
= 100 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).
Characteristic
LM2574−3.3
([Note 1] Test Circuit Figure 16)
Output Voltage (V
in
= 12 V, I
Load
= 100 mA, T
J
= 25°C)
Output Voltage (4.75 V
≤
V
in
≤
40 V, 0.1 A
≤
I
Load
≤
0.5 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 12 V, I
Load
= 0.5 A)
LM2574−5
([Note 1] Test Circuit Figure 16)
Output Voltage (V
in
= 12 V, I
Load
= 100 mA, T
J
= 25°C)
Output Voltage (7.0 V
≤
V
in
≤
40 V, 0.1 A
≤
I
Load
≤
0.5 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 12 V, I
Load
= 0.5 A)
LM2574−12
([Note 1] Test Circuit Figure 16)
Output Voltage (V
in
= 25 V, I
Load
= 100 mA, T
J
= 25°C)
Output Voltage (15 V
≤
V
in
≤
40 V, 0.1 A
≤
I
Load
≤
0.5 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 15 V, I
Load
= 0.5 A)
LM2574−15
([Note 1] Test Circuit Figure 16)
Output Voltage (V
in
= 30 V, I
Load
= 100 mA, T
J
= 25°C)
Output Voltage (18 V < V
in
< 40 V, 0.1 A < I
Load
< 0.5 A)
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 18 V, I
Load
= 0.5 A)
LM2574 ADJUSTABLE VERSION
([Note 1] Test Circuit Figure 16)
Feedback Voltage V
in
= 12 V, I
Load
= 100 mA, V
out
= 5.0 V, T
J
= 25°C
Feedback Voltage 7.0 V
≤
V
in
≤
40 V, 0.1 A
≤
I
Load
≤
0.5 A, V
out
= 5.0
V
T
J
= 25°C
T
J
= −40 to +125°C
Efficiency (V
in
= 12 V, I
Load
= 0.5 A, V
out
= 5.0 V)
V
FB
V
FBT
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
10
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
−
72
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 the switching regulator system performance.
When the LM2574 is used as shown in the Figure 16 test circuit, the system performance will be as shown in the system parameters section
of the Electrical Characteristics.
2. Tested junction temperature range for the LM2574, NCV2574: T
low
= −40°C T
high
= +125°C.
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3
LM2574, NCV2574
SYSTEM PARAMETERS
([Note 3] Test Circuit Figure 16)
ELECTRICAL CHARACTERISTICS (continued)
(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, V
in
= 30 V for the 15 V version. I
Load
= 100 mA. For typical values T
J
= 25°C, for
min/max values T
J
is the operating junction temperature range that applies [Note 4], unless otherwise noted).
Characteristic
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 5)
T
J
= 25°C
T
J
= 0 to +125°C
T
J
= −40 to +125°C
Saturation Voltage (I
out
= 0.5 A, [Note 6])
T
J
= 25°C
T
J
= −40 to +125°C
Max Duty Cycle (“on”) (Note 7)
Current Limit Peak Current (Notes 5 and 6)
T
J
= 25°C
T
J
= −40 to +125°C
Output Leakage Current (Notes 8 and 9), T
J
= 25°C
Output = 0 V
Output = − 1.0 V
Quiescent Current (Note 8)
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
V
out
= 0 V
T
J
= 25°C
T
J
= −40 to +125°C
Nominal Output Voltage
T
J
= 25°C
T
J
= −40 to +125°C
ON/OFF P
in
Input Current
ON/OFF P
in
= 5.0 V (“off”), T
J
= 25°C
ON/OFF P
in
= 0 V (“on”), T
J
= 25°C
I
b
−
−
f
O
−
47
42
V
sat
−
−
DC
I
CL
0.7
0.65
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
−
−
−
60
−
200
400
V
5.0
−
9.0
11
mA
0.6
10
2.0
30
mA
1.0
−
1.6
1.8
mA
93
1.0
−
98
1.2
1.4
−
%
A
52
52
−
−
58
63
V
25
−
100
200
kHz
nA
Symbol
Min
Typ
Max
Unit
3. External components such as the catch diode, inductor, input and output capacitors can affect the switching regulator system performance.
When the LM2574 is used as shown in the Figure 16 test circuit, the system performance will be as shown in the system parameters section
of the Electrical Characteristics.
4. Tested junction temperature range for the LM2574, NCV2574: T
low
= −40°C T
high
= +125°C.
5. 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 power dissipation of the
IC by lowering the minimum duty cycle from 5% down to approximately 2%.
6. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to the output pin.
7. Feedback (Pin 4) removed from output and connected to 0 V.
8. 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.
9. V
in
= 40 V.
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LM2574, NCV2574
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 16)
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
−25
0
25
60
75
100
125
V
in
= 20 V
I
Load
= 100 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
= 100 mA
T
J
= 25°C
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)
L = 300
mH
1.5
I
Load
= 500 mA
I O, OUTPUT CURRENT (A)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
V
in
= 25 V
1.0
I
Load
= 100 mA
0.5
0
−50
−25
0
25
60
75
100
125
0.7
−50
−25
0
25
60
75
100
125
T
J
, JUNCTION TEMPERATURE (°C)
T
J
, JUNCTION TEMPERATURE (°C)
Figure 4. Dropout Voltage
Figure 5. Current Limit
Istby , STANDBY QUIESCENT CURRENT (
μ
A)
20
IQ , 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
= 100 mA
I
Load
= 500 A
V
out
= 5.0 V
Measured at
Ground Pin
T
J
= 25°C
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
60
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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