LM2574/LM2574HV SIMPLE SWITCHER 0.5A Step-Down Voltage Regulator
June 1999
LM2574/LM2574HV
SIMPLE SWITCHER
™
0.5A Step-Down Voltage Regulator
General Description
The LM2574 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving a 0.5A load
with excellent line and load regulation. These devices are
available 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 frequency
compensation and a fixed-frequency oscillator.
The LM2574 series offers a high-efficiency replacement for
popular three-terminal linear regulators. Because of its high
efficiency, the copper traces on the printed circuit board are
normally the only heat sinking needed.
A standard series of inductors optimized for use with the
LM2574 are available from several different manufacturers.
This feature greatly simplifies the design of switch-mode
power supplies.
Other features include a guaranteed
±
4% tolerance on out-
put voltage within specified input voltages and output load
conditions, and
±
10% on the oscillator frequency. External
shutdown is included, featuring 50 µA (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
n
3.3V, 5V, 12V, 15V, and adjustable output versions
n
Adjustable version output voltage range, 1.23V to 37V
(57V for HV version)
±
4% max over line and load
conditions
n
Guaranteed 0.5A output current
n
Wide input voltage range, 40V, up to 60V for HV version
n
Requires only 4 external components
n
52 kHz fixed frequency internal oscillator
n
TTL shutdown capability, low power standby mode
n
High efficiency
n
Uses readily available standard inductors
n
Thermal shutdown and current limit protection
Applications
n
n
n
n
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to negative converter (Buck-Boost)
Typical Application
(Fixed Output Voltage Versions)
DS011394-1
Note:
Pin numbers are for 8-pin DIP package.
Patent Pending
SIMPLE SWITCHER
™
is a trademark of National Semiconductor Corporation
© 1999 National Semiconductor Corporation
DS011394
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Connection Diagrams
8-Lead DIP
14-Lead Wide
Surface Mount (WM)
DS011394-2
* No internal connection, but should be soldered to PC board for best heat
transfer.
Top View
Order Number LM2574-3.3HVN, LM2574HVN-5.0,
LM2574HVN-12, LM2574HVN-15, LM2574HVN-ADJ,
LM2574N-3.3, LM2574N-5.0, LM2574N-12,
LM2574N-15 or LM2574N-ADJ
See NS Package Number N08A
DS011394-3
Top View
Order Number LM2574HVM-3.3, LM2574HVM-5.0,
LM2574HVM-12, LM2574HVM-15, LM2574HVM-ADJ,
LM2574M-3.3 LM2574M-5.0, LM2574M-12,
LM2574M-15 or LM2574M-ADJ
See NS Package Number M14B
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2
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
LM2574
LM2574HV
ON /OFF Pin Input Voltage
Output Voltage to Ground
(Steady State)
Minimum ESD Rating
(C = 100 pF, R = 1.5 kΩ)
Storage Temperature Range
45V
63V
−0.3V
≤
V
≤
+V
IN
−1V
2 kV
−65˚C to +150˚C
Lead Temperature
(Soldering, 10 seconds)
Maximum Junction Temperature
Power Dissipation
260˚C
150˚C
Internally Limited
Operating Ratings
Temperature Range
LM2574/LM2574HV
Supply Voltage
LM2574
LM2574HV
−40˚C
≤
T
J
≤
+125˚C
40V
60V
LM2574-3.3, LM2574HV-3.3
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Symbol
Parameter
Conditions
Typ
SYSTEM PARAMETERS
(Note 3) Test Circuit
Figure 2
V
OUT
Output Voltage
V
IN
= 12V, I
LOAD
= 100 mA
LM2574-3.3
LM2574HV-3.3
Limit
(Note 2)
3.3
3.234
3.366
V
OUT
Output Voltage
LM2574
V
OUT
Output Voltage
LM2574HV
η
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
72
4.75V
≤
V
IN
≤
60V, 0.1A
≤
I
LOAD
≤
0.5A
3.3
3.168/3.135
3.450/3.482
V(Min)
V(Max)
%
4.75V
≤
V
IN
≤
40V, 0.1A
≤
I
LOAD
≤
0.5A
3.3
3.168/3.135
3.432/3.465
V
V(Min)
V(Max)
V
V(Min)
V(Max)
Units
(Limits)
LM2574-5.0, LM2574HV-5.0
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Symbol
Parameter
Conditions
Typ
SYSTEM PARAMETERS
(Note 3) Test Circuit
Figure 2
V
OUT
Output Voltage
V
IN
= 12V, I
LOAD
= 100 mA
LM2574-5.0
LM2574HV-5.0
Limit
(Note 2)
5
4.900
5.100
V
OUT
Output Voltage
LM2574
V
OUT
Output Voltage
LM2574HV
η
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
77
7V
≤
V
IN
≤
60V, 0.1A
≤
I
LOAD
≤
0.5A
5
4.800/4.750
5.225/5.275
V(Min)
V(Max)
%
7V
≤
V
IN
≤
40V, 0.1A
≤
I
LOAD
≤
0.5A
5
4.800/4.750
5.200/5.250
V
V(Min)
V(Max)
V
V(Min)
V(Max)
Units
(Limits)
3
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LM2574-12, LM2574HV-12
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Symbol
Parameter
Conditions
Typ
SYSTEM PARAMETERS
(Note 3) Test Circuit
Figure 2
V
OUT
Output Voltage
V
IN
= 25V, I
LOAD
= 100 mA
LM2574-12
LM2574HV-12
Limit
(Note 2)
12
11.76
12.24
V
OUT
Output Voltage
LM2574
V
OUT
Output Voltage
LM2574HV
η
Efficiency
V
IN
= 15V, I
LOAD
= 0.5A
88
15V
≤
V
IN
≤
60V, 0.1A
≤
I
LOAD
≤
0.5A
12
11.52/11.40
12.54/12.66
V(Min)
V(Max)
%
15V
≤
V
IN
≤
40V, 0.1A
≤
I
LOAD
≤
0.5A
12
11.52/11.40
12.48/12.60
V
V(Min)
V(Max)
V
V(Min)
V(Max)
Units
(Limits)
LM2574-15, LM2574HV-15
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Symbol
Parameter
Conditions
Typ
SYSTEM PARAMETERS
(Note 3) Test Circuit
Figure 2
V
OUT
Output Voltage
V
IN
= 30V, I
LOAD
= 100 mA
LM2574-15
LM2574HV-15
Limit
(Note 2)
15
14.70
15.30
V
OUT
Output Voltage
LM2574
V
OUT
Output Voltage
LM2574HV
η
Efficiency
V
IN
= 18V, I
LOAD
= 0.5A
88
18V
≤
V
IN
≤
60V, 0.1A
≤
I
LOAD
≤
0.5A
15
14.40/14.25
15.68/15.83
V(Min)
V(Max)
%
18V
≤
V
IN
≤
40V, 0.1A
≤
I
LOAD
≤
0.5A
15
14.40/14.25
15.60/15.75
V
V(Min)
V(Max)
V
V(Min)
V(Max)
Units
(Limits)
LM2574-ADJ, LM2574HV-ADJ
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Unless otherwise specified, V
IN
= 12V, I
LOAD
= 100 mA.
Symbol
Parameter
Conditions
Typ
SYSTEM PARAMETERS
(Note 3) Test Circuit
Figure 2
V
FB
Feedback Voltage
V
IN
= 12V, I
LOAD
= 100 mA
LM2574-ADJ
LM2574HV-ADJ
Limit
(Note 2)
1.230
1.217
1.243
V
V(Min)
V(Max)
Units
(Limits)
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4
LM2574-ADJ, LM2574HV-ADJ
Electrical Characteristics
(Continued)
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Unless otherwise specified, V
IN
= 12V, I
LOAD
= 100 mA.
Symbol
Parameter
Conditions
Typ
SYSTEM PARAMETERS
(Note 3) Test Circuit
Figure 2
V
FB
Feedback Voltage
LM2574
V
FB
Feedback Voltage
LM2574HV
η
Efficiency
7V
≤
V
IN
≤
40V, 0.1A
≤
I
LOAD
≤
0.5A
V
OUT
Programmed for 5V. Circuit of
Figure 2
7V
≤
V
IN
≤
60V, 0.1A
≤
I
LOAD
≤
0.5A
V
OUT
Programmed for 5V. Circuit of
Figure 2
V
IN
= 12V, V
OUT
= 5V, I
LOAD
= 0.5A
77
1.230
1.193/1.180
1.273/1.286
V(Min)
V(Max)
%
1.230
1.193/1.180
1.267/1.280
V
V(Min)
V(Max)
LM2574-ADJ
LM2574HV-ADJ
Limit
(Note 2)
Units
(Limits)
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Unless otherwise specified, V
IN
= 12V for the 3.3V, 5V, and Adjustable version, V
IN
= 25V for the 12V version,
and V
IN
= 30V for the 15V version. I
LOAD
= 100 mA.
Symbol
Parameter
Conditions
Typ
DEVICE PARAMETERS
I
b
f
O
Feedback Bias
Current
Oscillator Frequency
Adjustable Version Only, V
OUT
= 5V
(see Note 10)
50
52
47/42
58/63
V
SAT
DC
Saturation Voltage
Max Duty Cycle
(ON)
Current Limit
I
OUT
= 0.5A (Note 4)
(Note 5)
0.9
1.2/1.4
98
93
I
CL
Peak Current, (Notes 4, 10)
1.0
0.7/0.65
1.6/1.8
I
L
Output Leakage
Current
I
Q
I
STBY
θ
JA
θ
JA
θ
JA
θ
JA
Quiescent Current
Standby Quiescent
Current
Thermal Resistance
N Package, Junction to Ambient (Note 8)
N Package, Junction to Ambient (Note 9)
M Package, Junction to Ambient (Note 8)
M Package, Junction to Ambient (Note 9)
92
72
102
78
˚C/W
(Note 6)
ON /OFF Pin = 5V (OFF)
(Notes 6, 7)
Output = 0V
Output = −1V
Output = −1V
5
10
50
200
2
7.5
30
100/500
nA
kHz
kHz(Min)
kHz(Max)
V
V(max)
%
%(Min)
A
A(Min)
A(Max)
mA(Max)
mA
mA(Max)
mA
mA(Max)
µA
µA(Max)
LM2574-XX
LM2574HV-XX
Limit
(Note 2)
Units
(Limits)
5
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