ON Semiconductor LM2574, NCV2574 Technical data

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

16

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

• 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

* No internal connection, but should be soldered to

* PC board for best heat transfer.

• Pb−Free Packages are Available*

Applications

• Simple and High−Efficiency Step−Down (Buck) Regulators

• Efficient Pre−regulator for Linear Regulators

See detailed ordering and shipping information in the package
dimensions section on page 24 of this data sheet.

• On−Card Switching Regulators

• Positive to Negative Converters (Buck−Boost)

• Negative Step−Up Converters

DEVICE MARKING INFORMATION

See general marking information in the device marking
section on page 24 of this data sheet.

• Power Supply for Battery Chargers

*For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting

Techniques Reference Manual, SOLDERRM/D.

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SO−16 WB

DW SUFFIX

1

8

1

CASE 751G

PDIP−8

N SUFFIX

CASE 626

PIN CONNECTIONS

*

16

15

14

13

12

11

10

9

8

7

6

5

*
Output
*
V
*
*
*

*
Output

*
V

FB

Sig Gnd

/OFF

ON
Pwr Gnd

FB

Sig Gnd

ON

/OFF

Pwr Gnd

1

*

2

*

3

4

5

6

7

*

8

*

(Top View)

1

2

3

4

(Top View)

ORDERING INFORMATION

in

in

© Semiconductor Components Industries, LLC, 2006

August, 2006 − Rev. 8

1 Publication Order Number:

LM2574/D

Typical Application (Fixed Output Voltage Versions)

Unregulated

DC Input

LM2574, NCV2574

Feedback

(3)

(14)

/OFF3

1

Output

7

7.0 − 40 V

Unregulated

DC Input

C

22 mF

+V

in

LM2574

5

in

(12)

Sig

2

Gnd

Pwr

4ON

Gnd

(4) (6) (5)

Representative Block Diagram and Typical Application

+V

in

5

C

in

(12)

1

(3)

Feedback

Fixed Gain

R2

Error Amplifier

R1

1.0 k

Freq
Shift

18 kHz

Sig Gnd

2

1.235 V

Band−Gap

Reference

(4)

3.1 V Internal

Comparator

52 kHz

Oscillator

Regulator

Current

Latch

Reset

ON

Limit

/OFF

330 mH

D1
1N5819

Driver

Thermal

Shutdown

L1

C
220 mF

1.0 Amp
Switch

out

5.0 V Regulated
Output 0.5 A Load

ON

/OFF

3

Voltage Versions

(5)

For adjustable version
R1 = open, R2 = 0 W

Output

7

(14)

Pwr Gnd

4

(6)

Output

D1

3.3 V

5.0 V
12 V
15 V

L1

R2

(W)

1.7 k

3.1 k

8.84 k

11.3 k

V

out

C

out

Load

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 V
ON/OFF Pin Input Voltage − −0.3 V ≤ V ≤ +V
Output Voltage to Ground (Steady State) − −1.0 V
DW Suffix, Plastic Package Case 751G

Max Power Dissipation P

Thermal Resistance, Junction−to−Air

N Suffix, Plastic Package Case 626
Max Power Dissipation P

Thermal Resistance, Junction−to−Ambient

Thermal Resistance, Junction−to−Case
Storage Temperature Range T
Minimum ESD Rating − 2.0 kV

(Human Body Model: C = 100 pF, R = 1.5 kW)
Lead Temperature (Soldering, 10 seconds) − 260 °C

Maximum Junction Temperature T

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.

Symbol Value Unit

in

D

R

q

JA

D

R

q

JA

R

q

JC

stg

J

45 V

in

Internally Limited W

145 °C/W

Internally Limited W

100 °C/W

5.0 °C/W

−65°C to +150°C °C

150 °C

V

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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 T
Supply Voltage V

SYSTEM PARAMETERS ([Note 1] Test Circuit Figure 16)

ELECTRICAL CHARACTERISTICS (Unless otherwise specified, V

version, V
T

is the operating junction temperature range that applies [Note 2], unless otherwise noted).

J

LM2574−3.3 ([Note 1] Test Circuit Figure 16)

Output Voltage (V
Output Voltage (4.75 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

Efficiency (Vin = 12 V, I

LM2574−5 ([Note 1] Test Circuit Figure 16)

Output Voltage (Vin = 12 V, I
Output Voltage (7.0 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

Efficiency (Vin = 12 V, I

LM2574−12 ([Note 1] Test Circuit Figure 16)

Output Voltage (Vin = 25 V, I
Output Voltage (15 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

Efficiency (Vin = 15 V, I

LM2574−15 ([Note 1] Test Circuit Figure 16)

Output Voltage (V
Output Voltage (18 V < Vin < 40 V, 0.1 A < I

Efficiency (Vin = 18 V, I

LM2574 ADJUSTABLE VERSION ([Note 1] Test Circuit Figure 16)

Feedback Voltage Vin = 12 V, I
Feedback Voltage 7.0 V ≤ Vin ≤ 40 V, 0.1 A ≤ I

V

Efficiency (Vin = 12 V, I

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

= 25 V for the 12 V version, Vin = 30 V for the 15 V version. I

in

Characteristic

= 12 V, I

in

= 100 mA, TJ = 25°C) V

Load

≤ 0.5 A) V

Load

TJ = 25°C 3.168 3.3 3.432
TJ = −40 to +125°C 3.135 − 3.465

= 0.5 A) η − 72 − %

Load

= 100 mA, TJ = 25°C) V

Load

≤ 0.5 A) V

T

= 25°C

J

T

= −40 to +125°C

J

T

= 25°C

J

T

= −40 to +125°C

J

Load

Load

= 30 V, I

in

= 0.5 A) η − 77 − %

= 100 mA, TJ = 25°C) V

Load

= 0.5 A) η − 88 − %

= 100 mA, TJ = 25°C) V

Load

Load

≤ 0.5 A) V

Load

< 0.5 A) V

Load

TJ = 25°C 14.4 15 15.6
TJ = −40 to +125°C 14.25 15.75

= 0.5 A) η − 88 − %

Load

= 100 mA, V

Load

= 5.0 V, TJ = 25°C V

out

Load

≤ 0.5 A, V

out

= 5.0

TJ = 25°C 1.193 1.23 1.267
TJ = −40 to +125°C 1.18 1.28

= 0.5 A, V

Load

= 5.0 V) η − 77 − %

out

= 12 V for the 3.3 V, 5.0 V, and Adjustable

in

Load

= −40°C T

low

Symbol Value Unit

J

in

−40 to +125 °C
40 V

= 100 mA. For typical values TJ = 25°C, for min/max values

Symbol Min Typ Max Unit

out
out

out
out

3.234 3.3 3.366 V
V

4.9 5.0 5.1 V
V

4.8 5.0 5.2

4.75 5.25

out
out

11.76 10 12.24 V
V

11.52 12 12.48

11.4 − 12.6

14.7 15 15.3 V
V

1.217 1.23 1.243 V
V

V

out
out

FB

FBT

= +125°C.

high

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3

LM2574, NCV2574

SYSTEM PARAMETERS ([Note 3] Test Circuit Figure 16)

ELECTRICAL CHARACTERISTICS (continued) (Unless otherwise specified, V

Adjustable version, V
min/max values T

ALL OUTPUT VOLTAGE VERSIONS

Feedback Bias Current V

TJ = 25°C − 25 100
TJ = −40 to +125°C − − 200

Oscillator Frequency (Note 5) f

TJ = 25°C − 52 −
TJ = 0 to +125°C 47 52 58
TJ = −40 to +125°C 42 − 63

Saturation Voltage (I

TJ = 25°C − 1.0 1.2

TJ = −40 to +125°C − − 1.4
Max Duty Cycle (“on”) (Note 7) DC 93 98 − %
Current Limit Peak Current (Notes 5 and 6) I

TJ = 25°C 0.7 1.0 1.6

TJ = −40 to +125°C 0.65 − 1.8
Output Leakage Current (Notes 8 and 9), TJ = 25°C I

Output = 0 V − 0.6 2.0

Output = − 1.0 V − 10 30
Quiescent Current (Note 8) I

TJ = 25°C − 5.0 9.0

TJ = −40 to +125°C − − 11
Standby Quiescent Current (ON/OFF Pin = 5.0 V (“off”)) I

TJ = 25°C − 60 200

TJ = −40 to +125°C − − 400
ON/OFF Pin Logic Input Level V

V

= 0 V V

out

TJ = 25°C 2.2 1.4 −

TJ = −40 to +125°C 2.4 − −

Nominal Output Voltage V

TJ = 25°C − 1.2 1.0

TJ = −40 to +125°C − − 0.8
ON/OFF Pin Input Current

ON/OFF Pin = 5.0 V (“off”), T

ON/OFF Pin = 0 V (“on”), TJ = 25°C I

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

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.

= 40 V.

9. V

in

= 25 V for the 12 V version, Vin = 30 V for the 15 V version. I

in

is the operating junction temperature range that applies [Note 4], unless otherwise noted).

J

Characteristic

= 5.0 V (Adjustable Version Only) I

out

= 0.5 A, [Note 6]) V

out

= 25°C I

J

low

Symbol Min Typ Max Unit

O

sat

CL

Q

stby

IH
IL

= −40°C T

= 12 V for the 3.3 V, 5.0 V, and

in

= 100 mA. For typical values TJ = 25°C, for

Load

b

L

IH

IL

− 15 30

− 0 5.0

= +125°C.

high

nA

kHz

V

A

mA

mA

mA

mA

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4

LM2574, NCV2574

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16)

1.0

Vin = 20 V

0.8
I

Load

0.6
Normalized at TJ = 25°C

0.4

0.2

0

−0.2

−0.4

−0.6

, OUTPUT VOLTAGE CHANGE (%)

out

−0.8

V

−1.0

2.0

L = 300 mH

1.5

1.0

0.5

INPUT − OUTPUT DIFFERENTIAL (V)

0

= 100 mA

TJ, JUNCTION TEMPERATURE (°C)

Figure 2. Normalized Output Voltage

I

= 500 mA

Load

I

= 100 mA

Load

TJ, JUNCTION TEMPERATURE (°C)

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

−0.2

, OUTPUT VOLTAGE CHANGE (%)

out

−0.4

V

1251007560250−25−50 403530252015105.00

−0.6

1.4

1.3

1.2

1.1

1.0

0.9

, OUTPUT CURRENT (A)

O

I

0.8

1251007560250−25−50 1251007560250−25−50

0.7

I

Load

T

= 25°C

J

= 100 mA

3.3 V, 5.0 V and ADJ

, INPUT VOLTAGE (V)

V

in

Figure 3. Line Regulation

TJ, JUNCTION TEMPERATURE (°C)

12 V and 15 V

Vin = 25 V

, QUIESCENT CURRENT (mA)

Q

I

8.0

6.0

4.0

Figure 4. Dropout Voltage Figure 5. Current Limit

, STANDBY QUIESCENT CURRENT ( A)μ

I

stby

200

180

160

140

120

100

V

= 5.0 V

ON/OFF

Vin = 40 V

80

60

40

Vin = 12 V

20

0

TJ, JUNCTION TEMPERATURE (°C)

20

V

= 5.0 V

18

16

14

I

12

Load

= 500 A

out

Measured at
Ground Pin
T

= 25°C

J

10

I

= 100 mA

Load

403530252015105.00 1251007560250−25−50

V

, INPUT VOLTAGE (V)

in

Figure 6. Quiescent Current Figure 7. Standby Quiescent Current

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5

LM2574, NCV2574

out

s

out

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16) (continued)

8.0

6.0

Vin = 12 V
Normalized at 25°C

4.0

2.0

0

−2.0

−4.0

−6.0

NORMALIZED FREQUENCY (%)

−8.0

10

TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50 0 0.1 0.2 0.3 0.4 0.5

Figure 8. Oscillator Frequency

5.0

4.5

4.0

3.5

3.0

2.5

2.0

, INPUT VOLTAGE (V)V

1.5

in

1.0

0.5

0

Vin = 1.23 V
I

= 100 mA

Load

TJ, JUNCTION TEMPERATURE (°C)

Adjustable Version Only

1251007550250−25−50 1251007550250−25−50

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

, SATURATION VOLTAGE (V)

0.5

sat

V

0.4

0.3

100

80

60

40

20

0

−20

−40

−60

, FEEDBACK PIN CURRENT (nA)

FB

I

−80

−100

−40°C

25°C

125°C

Figure 9. Switch Saturation Voltage

, JUNCTION TEMPERATURE (°C)

T

J

Figure 10. Minimum Operating Voltage Figure 11. Feedback Pin Current

SWITCH CURRENT (A)

Adjustable Version Only

20 V

A

10 V

0

0.6 A

0.4 A

B

0.2 A

0

20 mV

C

AC

5 ms/DIV

A: Output Pin Voltage, 10 V/DIV.
B: Inductor Current, 0.2 A/DIV.
C: Output Ripple Voltage, 20 mV/DIV, AC−Coupled

Figure 12. Continuous Mode Switching Waveforms

V

= 5.0 V, 500 mA Load Current, L = 330 mH

A

B

20 mV

C

Figure 13. Discontinuous Mode Switching Waveform

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6

20 V

10 V

0

0.4 A

0.2 A

0

AC

5 ms/DIV

A: Output Pin Voltage, 10 V/DIV.
B: Inductor Current, 0.2 A/DIV.
C: Output Ripple Voltage, 20 mV/DIV, AC−Coupled

V

= 5.0 V, 100 mA Load Current, L = 100 mH

LM2574, NCV2574

out

out

F

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16) (continued)

50 mV

A

AC

50 mV

A

AC

500 mA

B

0

A: Output Voltage, 50 mV/DIV, AC Coupled
B: 100 mA to 500 mA Load Pulse

Figure 14. 500 mA Load Transient Response for

Continuous Mode Operation, L = 330 mH, C

= 300 mF

200 mA

B

100 mA

0

200 ms/DIV200 ms/DIV

A: Output Voltage, 50 mV/DIV, AC Coupled
B: 50 mA to 250 mA Load Pulse

Figure 15. 250 mA Load Transient Response for

Discontinuous Mode Operation, L = 68 mH, C

= 470 m

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7

Fixed Output Voltage Versions

7.0 − 40 V

Unregulated

DC Input

LM2574, NCV2574

(3)

V

in

1

(12)

C

in

22 mF

Cin−22 mF, 60 V, Aluminium Electrolytic

− 220 mF, 25 V, Aluminium Electrolytic

C

out

D1 − Schottky, 1N5819
L1 − 330 mH, (For 5.0 V
R1 − 2.0 k, 0.1%
R2 − 6.12 k, 0.1%

LM2574

Fixed Output

2 Sig

Gnd

Gnd

(6) (4)

(14)

34ON

, 3.3 V

in

out

Feedback

1

Output

7

/OFFPwr

(5)

, use 100 mH)

L1

330 mH

D1
1N5819

C

out

220 mF

V

out

Load

7.0 V − 40 V
Unregulated

DC Input

V

in

1

C

in

22 mF

Adjustable Output Voltage Versions

Feedback

(3)

(14)

34ON/OFFPwr

+ V

ref

= 1.23 V, R1

ref

(5)

V

V

1

Output

7

ǒ

1.0 )

out

ref

–1.0Ǔ

R2
R1

Ǔ

LM2574

Adjustable

(12)

2 Sig

Gnd

NOTE: Pin numbers in ( ) are for the SO−16W package.

Gnd

(6) (4)

V

out

R2 + R1ǒ

Where V
between 1.0 kW and 5.0 kW

Figure 16. Test Circuit and Layout Guidelines

L1

330 mH

D1
1N5819

C

out

220 mF

R2

6.12 k

R1

2.0 k

V

5.0 V

Load

out

PCB LAYOUT GUIDELINES

As in any switching regulator, the layout of the printed
circuit board is very important. Rapidly switching currents
associated with wiring inductance, stray capacitance and
parasitic inductance of the printed circuit board traces can
generate voltage transients which can generate
electromagnetic interferences (EMI) and affect the desired
operation. As indicated in the Figure 16, to minimize
inductance and ground loops, the length of the leads
indicated by heavy lines should be kept as short as possible.

For best results, single−point grounding (as indicated) or
ground plane construction should be used.

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On the other hand, the PCB area connected to the Pin 7
(emitter of the internal switch) of the LM2574 should be
kept to a minimum in order to minimize coupling to sensitive
circuitry.

Another sensitive part of the circuit is the feedback. It is
important to keep the sensitive feedback wiring short. To
assure this, physically locate the programming resistors near
to the regulator, when using the adjustable version of the
LM2574 regulator.

8