National Semiconductor LM2574, LM2574HV Technical data

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LM2574/LM2574HV
SIMPLE SWITCHER

™

0.5A Step-Down Voltage Regulator

LM2574/LM2574HV SIMPLE SWITCHER 0.5A Step-Down Voltage Regulator

June 1999

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 aminimumnumber 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
put voltage within specified input voltages and output load
conditions, and
shutdown is included, featuring 50 µA (typical) standby cur­rent. The output switch includes cycle-by-cycle current limit­ing, as well as thermal shutdown for full protection under
fault conditions.

±

10%on the oscillator frequency. External

±

4%tolerance on out-

Features

n 3.3V, 5V, 12V, 15V, and adjustable output versions
n Adjustable version output voltage range, 1.23V to 37V

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 Simple high-efficiency step-down (buck) regulator
n Efficient pre-regulator for linear regulators
n On-card switching regulators
n Positive to negative converter (Buck-Boost)

Typical Application (Fixed Output Voltage Versions)

(57V for HV version)
conditions

±

4%max over line and load

Note: Pin numbers are for 8-pin DIP package.

Patent Pending
SIMPLE SWITCHER

© 1999 National Semiconductor Corporation DS011394 www.national.com

™

is a trademark of National Semiconductor Corporation

DS011394-1

Connection Diagrams

8-Lead DIP

* No internal connection, but should be soldered to PC board for best heat
transfer.

DS011394-2

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

14-Lead Wide

Surface Mount (WM)

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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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 45V

LM2574HV 63V
ON /OFF Pin Input Voltage
Output Voltage to Ground

(Steady State) −1V
Minimum ESD Rating

−0.3V ≤ V ≤ +V

Lead Temperature

(Soldering, 10 seconds) 260˚C
Maximum Junction Temperature 150˚C
Power Dissipation Internally Limited

Operating Ratings

Temperature Range

IN

LM2574/LM2574HV −40˚C ≤ T
Supply Voltage

LM2574 40V

LM2574HV 60V

≤ +125˚C

J

(C=100 pF, R=1.5 kΩ)2kV

Storage Temperature Range −65˚C to +150˚C

LM2574-3.3, LM2574HV-3.3
Electrical Characteristics

12V, I

12V, I

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

LM2574HV-3.3

Typ Limit

(Note 2)

Figure 2

=

100 mA 3.3 V

LOAD

3.234 V(Min)

3.366 V(Max)

≤ 0.5A 3.3 V

LOAD

3.432/3.465 V(Max)

≤ 0.5A 3.3

LOAD

3.450/3.482 V(Max)

=

0.5A 72

LOAD

(Limits)

%

Specifications with standard type face are for T

ture Range.

Symbol Parameter Conditions LM2574-3.3 Units

SYSTEM PARAMETERS (Note 3) Test Circuit

V

OUT

V

OUT

Output Voltage V

Output Voltage 4.75V ≤ VIN≤ 40V, 0.1A ≤ I

=

IN

LM2574 3.168/3.135 V(Min)

V

OUT

Output Voltage 4.75V ≤ VIN≤ 60V, 0.1A ≤ I
LM2574HV 3.168/3.135 V(Min)

η Efficiency V

=

IN

LM2574-5.0, LM2574HV-5.0
Electrical Characteristics

12V, I

12V, I

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

LM2574HV-5.0

Typ Limit

(Note 2)

Figure 2

=

100 mA 5 V

LOAD

4.900 V(Min)

5.100 V(Max)

≤ 0.5A 5 V

LOAD

5.200/5.250 V(Max)

≤ 0.5A 5

LOAD

5.225/5.275 V(Max)

=

0.5A 77

LOAD

(Limits)

%

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Specifications with standard type face are for T

ture Range.

Symbol Parameter Conditions LM2574-5.0 Units

SYSTEM PARAMETERS (Note 3) Test Circuit

V

OUT

V

OUT

Output Voltage V

Output Voltage 7V ≤ VIN≤ 40V, 0.1A ≤ I

=

IN

LM2574 4.800/4.750 V(Min)

V

OUT

Output Voltage 7V ≤ VIN≤ 60V, 0.1A ≤ I
LM2574HV 4.800/4.750 V(Min)

η Efficiency V

=

IN

LM2574-12, LM2574HV-12
Electrical Characteristics

25V, I

15V, I

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

LM2574HV-12

Typ Limit

(Note 2)

Figure 2

=

100 mA 12 V

LOAD

11.76 V(Min)

12.24 V(Max)

≤ 0.5A 12 V

LOAD

12.48/12.60 V(Max)

≤ 0.5A 12

LOAD

12.54/12.66 V(Max)

=

0.5A 88

LOAD

(Limits)

%

Specifications with standard type face are for T

ture Range.

Symbol Parameter Conditions LM2574-12 Units

SYSTEM PARAMETERS (Note 3) Test Circuit

V

OUT

V

OUT

Output Voltage V

Output Voltage 15V ≤ VIN≤ 40V, 0.1A ≤ I

=

IN

LM2574 11.52/11.40 V(Min)

V

OUT

Output Voltage 15V ≤ VIN≤ 60V, 0.1A ≤ I
LM2574HV 11.52/11.40 V(Min)

η Efficiency V

=

IN

LM2574-15, LM2574HV-15
Electrical Characteristics

30V, I

18V, I

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

LM2574HV-15

Typ Limit

(Note 2)

Figure 2

=

100 mA 15 V

LOAD

14.70 V(Min)

15.30 V(Max)

≤ 0.5A 15 V

LOAD

15.60/15.75 V(Max)

≤ 0.5A 15

LOAD

15.68/15.83 V(Max)

=

0.5A 88

LOAD

(Limits)

%

Specifications with standard type face are for T

ture Range.

Symbol Parameter Conditions LM2574-15 Units

SYSTEM PARAMETERS (Note 3) Test Circuit

V

OUT

V

OUT

Output Voltage V

Output Voltage 18V ≤ VIN≤ 40V, 0.1A ≤ I

=

IN

LM2574 14.40/14.25 V(Min)

V

OUT

Output Voltage 18V ≤ VIN≤ 60V, 0.1A ≤ I
LM2574HV 14.40/14.25 V(Min)

η Efficiency V

=

IN

LM2574-ADJ, LM2574HV-ADJ
Electrical Characteristics

Specifications with standard type face are for T

ture Range. Unless otherwise specified, V

Symbol Parameter Conditions LM2574-ADJ Units

SYSTEM PARAMETERS (Note 3) Test Circuit

V

FB

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Feedback Voltage V

=

IN

IN

12V, I

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

=

12V, I

LOAD

=

100 mA.

LM2574HV-ADJ

Typ Limit

(Note 2)

Figure 2

=

100 mA 1.230 V

LOAD

1.217 V(Min)

1.243 V(Max)

(Limits)

LM2574-ADJ, LM2574HV-ADJ
Electrical Characteristics

Specifications with standard type face are for T

ture Range. Unless otherwise specified, V

Symbol Parameter Conditions LM2574-ADJ Units

SYSTEM PARAMETERS (Note 3) Test Circuit

V

FB

V

FB

η Efficiency V

Feedback Voltage 7V ≤ VIN≤ 40V, 0.1A ≤ I
LM2574 V

Feedback Voltage 7V ≤ VIN≤ 60V, 0.1A ≤ I
LM2574HV V

(Continued)

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

=

12V, I

IN

LOAD

=

Figure 2

Programmed for 5V. Circuit of

OUT

Programmed for 5V. Circuit of

OUT

=

12V, V

IN

OUT

LOAD

LOAD

=

5V, I

LOAD

100 mA.

LM2574HV-ADJ

Typ Limit

(Note 2)

≤ 0.5A 1.230 V

Figure 2

1.193/1.180 V(Min)

1.267/1.280 V(Max)

≤ 0.5A 1.230

Figure 2

1.193/1.180 V(Min)

1.273/1.286 V(Max)

=

0.5A 77

(Limits)

%

All Output Voltage Versions
Electrical Characteristics

Specifications with standard type face are for T

ture Range. Unless otherwise specified, V

=

and V

30V for the 15V version. I

IN

LOAD

Symbol Parameter Conditions LM2574-XX Units

DEVICE PARAMETERS

I

b

f

O

V

SAT

Feedback Bias
Current

Oscillator Frequency (see Note 10) 52 kHz

Saturation Voltage I

DC Max Duty Cycle

Adjustable Version Only, V

OUT

(Note 5) 98

(ON)

I

CL

I

L

Current Limit Peak Current, (Notes 4, 10) 1.0 A

Output Leakage (Notes 6, 7) Output=0V 2 mA(Max)
Current Output=−1V 7.5 mA

I

Q

I

STBY

Quiescent Current (Note 6) 5 mA

Standby Quiescent ON /OFF Pin=5V (OFF) 50 µA
Current 200 µA(Max)

θ

JA

θ

JA

θ

JA

θ

JA

Thermal Resistance N Package, Junction to Ambient (Note 8) 92

N Package, Junction to Ambient (Note 9) 72 ˚C/W
M Package, Junction to Ambient (Note 8) 102
M Package, Junction to Ambient (Note 9) 78

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

=

12V for the 3.3V, 5V, and Adjustable version, V

IN

=

100 mA.

=

25V for the 12V version,

IN

LM2574HV-XX

Typ Limit

(Note 2)

=

5V 50 100/500 nA

OUT

47/42 kHz(Min)
58/63 kHz(Max)

=

0.5A (Note 4) 0.9 V

1.2/1.4 V(max)

93

0.7/0.65 A(Min)

1.6/1.8 A(Max)

Output=−1V 30 mA(Max)

10 mA(Max)

(Limits)

%

%

(Min)

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All Output Voltage Versions
Electrical Characteristics

Specifications with standard type face are for T
ture Range. Unless otherwise specified, V

=

and V

Symbol Parameter Conditions LM2574-XX Units

ON /OFF CONTROL Test Circuit

V

IH

V

IL

I

H

I

IL

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.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.

Note 2: All limits guaranteed at room temperature (Standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%produc-
tion tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate
Average Outgoing Quality Level.

Note 3: External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the LM2574
is used as shown in the

Note 4: Output pin sourcing current. No diode, inductor or capacitor connected to output pin.
Note 5: Feedback pin removed from output and connected to 0V.
Note 6: Feedback pin removed from output and connected to +12V for the Adjustable, 3.3V, and 5V versions, and +25V for the 12V and 15V versions, to force the

output transistor OFF.

Note 7: V
Note 8: Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will

lower thermal resistance further. See application hints in this data sheet and the thermal model in Switchers Made Simple software.
Note 9: Junction to ambient thermal resistance with approximately 4 square inches of 1 oz. (0.0014 in. thick) printed circuit board copper surrounding the leads. Ad-

ditional copper area will lower thermal resistance further. (See Note 8.)
Note 10: 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%.

30V for the 15V version. I

IN

Figure 2

ON /OFF Pin Logic V
Input Level V
ON /OFF Pin Input ON /OFF Pin=5V (OFF) 12 µA
Current 30 µA(Max)

Figure 2

test circuit, system performance will be as shown in system parameters section of Electrical Characteristics.

=

40V (60V for high voltage version).

IN

(Continued)

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

LOAD

=

12V for the 3.3V, 5V, and Adjustable version, V

IN

=

100 mA.

=

25V for the 12V version,

IN

LM2574HV-XX

(Limits)

Typ Limit

(Note 2)

=

0V 1.4 2.2/2.4 V(Min)

OUT

=

Nominal Output Voltage 1.2 1.0/0.8 V(Max)

OUT

ON /OFF Pin=0V (ON) 0µA

10 µA(Max)

Typical Performance Characteristics (Circuit of

Normalized Output Voltage

DS011394-27

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Line Regulation

Figure 2

DS011394-28

)

Dropout Voltage

DS011394-29

Typical Performance Characteristics (Circuit of

Figure 2

) (Continued)

Current Limit

Oscillator Frequency

Minimum Operating Voltage

DS011394-30

DS011394-33

Supply Current

Switch Saturation
Voltage

Supply Current
vs Duty Cycle

Standby
Quiescent Current

DS011394-31

DS011394-32

Efficiency

DS011394-35

DS011394-34

Feedback Voltage
vs Duty Cycle

DS011394-36

DS011394-37

DS011394-38

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Typical Performance Characteristics (Circuit of

Figure 2

) (Continued)

Feedback
Pin Current

DS011394-39

Continuous Mode Switching Waveforms

=

V

5V, 500 mA Load Current, L=330 µH

OUT

Notes:

A: Output Pin Voltage, 10V/div
B: Inductor Current, 0.2 A/div
C: Output Ripple Voltage, 20 mV/div,
AC-Coupled
Horizontal Time Base: 5 µs/div

DS011394-6

Junction to Ambient
Thermal Resistance

DS011394-40

Discontinuous Mode Switching Waveforms

=

V

5V, 100 mA Load Current, L=100 µH

OUT

Notes:

A: Output Pin Voltage, 10V/div
B: Inductor Current, 0.2 A/div
C: Output Ripple Voltage, 20 mV/div,
AC-Coupled
Horizontal Time Base: 5 µs/div

DS011394-7

500 mA Load Transient Response for Continuous
Mode Operation. L=330 µH, C

Notes:

A: Output Voltage, 50 mV/div.
AC Coupled
B: 100 mA to 500 mA Load Pulse
Horizontal Time Base: 200 µs/div

OUT

=

300 µF

DS011394-8

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250 mA Load Transient Response for Discontinuous
Mode Operation. L=68 µH, C

Notes:

A: Output Voltage, 50 mV/div.
AC Coupled
B: 50 mA to 250 mA Load Pulse
Horizontal Time Base: 200 µs/div

OUT

=

470 µF

DS011394-9