LM2576D2TR4-012G_技术文档

LM2576

3.0 A, 15 V, Step−Down

Switching Regulator

The LM2576 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 3.0 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.

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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 LM2576 are offered by several

different inductor manufacturers.

TO−220

TV SUFFIX

CASE 314B

1

5

Since the LM2576 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 many cases, the power dissipated is so low that no heatsink is

required or its size could be reduced dramatically.

Heatsink surface connected to Pin 3

A standard series of inductors optimized for use with the LM2576

are available from several different manufacturers. This feature

greatly simplifies the design of switch−mode power supplies.

The LM2576 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 80 mA (typical) standby current. The

output switch includes cycle−by−cycle current limiting, as well as

thermal shutdown for full protection under fault conditions.

TO−220

T SUFFIX

CASE 314D

1

5

Pin 1.

V

in

2. Output

3. Ground

4. Feedback

5. ON/OFF

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%

Maximum Over Line and Load Conditions

• Guaranteed 3.0 A Output Current

2

D PAK

D2T SUFFIX

CASE 936A

• Wide Input Voltage Range

1

• 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

• Moisture Sensitivity Level (MSL) Equals 1

• Pb−Free Packages are Available

5

Heatsink surface (shown as terminal 6 in

case outline drawing) is connected to Pin 3

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 25 of this data sheet.

Applications

• Simple High−Efficiency Step−Down (Buck) Regulator

• Efficient Pre−Regulator for Linear Regulators

• On−Card Switching Regulators

• Positive to Negative Converter (Buck−Boost)

• Negative Step−Up Converters

• Power Supply for Battery Chargers

©

Semiconductor Components Industries, LLC, 2006

1

Publication Order Number:

January, 2006 − Rev. 8

LM2576/D

LM2576

Typical Application (Fixed Output Voltage Versions)

Feedback

4

L1

100 mH

7.0 V − 40 V

Unregulated

DC Input

+V

in

LM2576

Output

2

1

5.0 V Regulated

Output 3.0 A Load

C

100 mF

in

D1

1N5822

C

out

1000 mF

3

GN

D

5

ON/OFF

Representative Block Diagram and Typical Application

+V

in

ON/OFF

Unregulated

DC Input

3.1 V Internal

Regulator

Output

Voltage Versions

R2

(W)

ON/OFF

1

5

C

3.3 V

5.0 V

12 V

15 V

1.7 k

3.1 k

8.84 k

11.3 k

in

4

Feedback

Current

Limit

For adjustable version

R1 = open, R2 = 0 W

R2

Fixed Gain

Error Amplifier

Comparator

Driver

Regulated

Output

R1

1.0 k

Latch

Freq

Shift

L1

V

out

Output

18 kHz

1.0 Amp

Switch

2

GND

1.235 V

Band−Gap

Reference

C

D1

out

Thermal

Shutdown

52 kHz

Oscillator

3

Reset

Load

This device contains 162 active transistors.

Figure 1. Block Diagram and Typical Application

MAXIMUM RATINGS

Rating

Symbol

Value

45

Unit

Maximum Supply Voltage

ON/OFF Pin Input Voltage

V

in

V

−

−0.3 V ≤ V ≤ +V

−1.0

in

Output Voltage to Ground (Steady−State)

−

Power Dissipation

Case 314B and 314D (TO−220, 5−Lead)

Thermal Resistance, Junction−to−Ambient

Thermal Resistance, Junction−to−Case

P

Internally Limited

W

D

R

65

5.0

°C/W

W

q

JA

JC

D

q

2

Case 936A (D PAK)

P

Internally Limited

Thermal Resistance, Junction−to−Ambient

Thermal Resistance, Junction−to−Case

R

70

5.0

°C/W

q

JA

JC

R

q

Storage Temperature Range

T

−65 to +150

2.0

°C

kV

°C

stg

Minimum ESD Rating (Human Body Model: C = 100 pF, R = 1.5 kW)

Lead Temperature (Soldering, 10 seconds)

Maximum Junction Temperature

−

260

T

150

J

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.

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2

LM2576

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

Symbol

Value

−40 to +125

40

Unit

°C

T

J

Supply Voltage

V

in

V

SYSTEM PARAMETERS (Note 1 Test Circuit Figure 15)

ELECTRICAL CHARACTERISTICS (Unless otherwise specified, V = 12 V for the 3.3 V, 5.0 V, and Adjustable version, V = 25 V

in

for the 12 V version, and V = 30 V for the 15 V version. I

= 500 mA. For typical values T = 25°C, for min/max values T is the

in

Load

J

operating junction temperature range that applies Note 2, unless otherwise noted.)

Characteristics

Symbol

Min

Typ

Max

Unit

LM2576−3.3 (Note 1 Test Circuit Figure 15)

Output Voltage (V = 12 V, I

= 0.5 A, T = 25°C)

V

out

3.234

3.3

3.366

V

in

Load

J

Output Voltage (6.0 V ≤ V ≤ 40 V, 0.5 A ≤ I

≤ 3.0 A)

V

out

in

Load

T = 25°C

T = −40 to +125°C

J

3.168

3.135

3.3

−

3.432

3.465

J

Efficiency (V = 12 V, I

= 3.0 A)

η

−

75

−

%

in

Load

LM2576−5 (Note 1 Test Circuit Figure 15)

Output Voltage (V = 12 V, I = 0.5 A, T = 25°C)

V

out

4.9

5.0

5.1

V

in

Load

J

Output Voltage (8.0 V ≤ V ≤ 40 V, 0.5 A ≤ I

≤ 3.0 A)

V

out

in

Load

T = 25°C

T = −40 to +125°C

J

4.8

4.75

5.0

−

5.2

5.25

J

Efficiency (V = 12 V, I

= 3.0 A)

Load

η

−

77

−

%

in

LM2576−12 (Note 1 Test Circuit Figure 15)

Output Voltage (V = 25 V, I = 0.5 A, T = 25°C)

V

out

11.76

12

12.24

V

in

Load

J

Output Voltage (15 V ≤ V ≤ 40 V, 0.5 A ≤ I

≤ 3.0 A)

V

out

in

Load

T = 25°C

T = −40 to +125°C

J

11.52

11.4

12

−

12.48

12.6

J

Efficiency (V = 15 V, I

= 3.0 A)

Load

η

−

88

−

%

in

LM2576−15 (Note 1 Test Circuit Figure 15)

Output Voltage (V = 30 V, I = 0.5 A, T = 25°C)

V

out

14.7

15

15.3

V

in

Load

J

Output Voltage (18 V ≤ V ≤ 40 V, 0.5 A ≤ I

≤ 3.0 A)

V

out

in

Load

T = 25°C

T = −40 to +125°C

J

14.4

14.25

15

−

15.6

15.75

J

Efficiency (V = 18 V, I

= 3.0 A)

Load

η

−

88

−

%

in

LM2576 ADJUSTABLE VERSION (Note 1 Test Circuit Figure 15)

Feedback Voltage (V = 12 V, I

= 0.5 A, V = 5.0 V, T = 25°C)

V

out

1.217

1.23

1.243

V

in

Load

out

J

Feedback Voltage (8.0 V ≤ V ≤ 40 V, 0.5 A ≤ I

≤ 3.0 A, V = 5.0 V)

V

out

in

Load

out

T = 25°C

T = −40 to +125°C

J

1.193

1.18

1.23

−

1.267

1.28

J

Efficiency (V = 12 V, I

= 3.0 A, V = 5.0 V)

η

−

77

−

%

in

Load

out

1. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance.

When the LM2576 is used as shown in the Figure 15 test circuit, system performance will be as shown in system parameters section.

2. Tested junction temperature range for the LM2576:

T

= −40°C

T

= +125°C

low

high

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3

LM2576

DEVICE PARAMETERS

ELECTRICAL CHARACTERISTICS (Unless otherwise specified, V = 12 V for the 3.3 V, 5.0 V, and Adjustable version, V = 25 V

in

for the 12 V version, and V = 30 V for the 15 V version. I

= 500 mA. For typical values T = 25°C, for min/max values T is the

in

Load

J

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

Characteristics Symbol

ALL OUTPUT VOLTAGE VERSIONS

Min

Typ

Max

Unit

Feedback Bias Current (V = 5.0 V Adjustable Version Only)

I

nA

out

b

T = 25°C

T = −40 to +125°C

J

−

25

−

100

200

J

Oscillator Frequency Note 3

f

kHz

V

osc

T = 25°C

−

47

42

52

−

58

63

J

T = 0 to +125°C

J

T = −40 to +125°C

J

Saturation Voltage (I = 3.0 A Note 4)

V

sat

out

T = 25°C

T = −40 to +125°C

J

−

1.5

−

1.8

2.0

J

Max Duty Cycle (“on”) Note 5

DC

94

98

−

%

A

Current Limit (Peak Current Notes 3 and 4)

I

CL

T = 25°C

T = −40 to +125°C

J

4.2

3.5

5.8

−

6.9

7.5

J

Output Leakage Current Notes 6 and 7, T = 25°C

Output = 0 V

Output = −1.0 V

I

mA

V

J

L

−

0.8

6.0

2.0

20

Quiescent Current Note 6

I

Q

T = 25°C

−

5.0

−

9.0

11

J

T = −40 to +125°C

J

Standby Quiescent Current (ON/OFF Pin = 5.0 V (“off”))

I

stby

T = 25°C

−

80

−

200

400

J

T = −40 to +125°C

J

ON/OFF Pin Logic Input Level (Test Circuit Figure 15)

V

out

= 0 V

V

IH

T = 25°C

T = −40 to +125°C

J

2.2

2.4

1.4

−

J

V

out

= Nominal Output Voltage

V

IL

T = 25°C

T = −40 to +125°C

J

−

1.2

−

1.0

0.8

J

ON/OFF Pin Input Current (Test Circuit Figure 15)

mA

ON/OFF Pin = 5.0 V (“off”), T = 25°C

I

−

15

0

30

5.0

J

IH

ON/OFF Pin = 0 V (“on”), T = 25°C

J

IL

3. 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 dissipation of the IC by

lowering the minimum duty cycle from 5% down to approximately 2%.

4. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to output pin.

5. Feedback (Pin 4) removed from output and connected to 0 V.

6. 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”.

7. V = 40 V.

in

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4

LM2576

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)

1.0

0.8

0.6

1.4

1.2

V

= 20 V

= 500 mA

in

I

= 500 mA

Load

I

Load

T = 25°C

J

1.0

0.8

0.6

0.4

Normalized at T = 25°C

J

0.4

0.2

3.3 V, 5.0 V and ADJ

0

−0.2

−0.4

0.2

0

12 V and 15 V

−0.2

−0.4

−0.6

−0.8

−1.0

−50

−25

0

25

50

75

100

125

0

5.0

10

15

20

25

30

35

40

T , JUNCTION TEMPERATURE (°C)

J

V , INPUT VOLTAGE (V)

in

Figure 2. Normalized Output Voltage

Figure 3. Line Regulation

2.0

1.5

1.0

0.5

0

6.5

6.0

5.5

V

in

= 25 V

I

= 3.0 A

Load

5.0

4.5

4.0

I

= 500 mA

Load

L1 = 150 mH

= 0.1 W

R

ind

−50

−25

0

25

50

75

100

125

−50

−25

0

25

50

75

100

125

T , JUNCTION TEMPERATURE (°C)

J

T , JUNCTION TEMPERATURE (°C)

J

Figure 4. Dropout Voltage

Figure 5. Current Limit

20

18

200

V

= 5.0 V

V

= 5.0 V

out

180

160

140

120

100

80

ON/OFF

Measured at

Ground Pin

T = 25°C

J

16

14

V

in

= 40 V

I

= 3.0 A

Load

12

10

V

in

= 12 V

60

I

= 200 mA

Load

8.0

6.0

4.0

40

20

0

−50

0

5.0

10

15

20

25

30

35

40

−25

0

25

50

75

100

125

V , INPUT VOLTAGE (V)

in

T , JUNCTION TEMPERATURE (°C)

J

Figure 6. Quiescent Current

Figure 7. Standby Quiescent Current

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5

LM2576

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)

200

180

160

140

120

1.6

1.4

1.2

T = 25°C

J

−40°C

1.0

100

80

0.8 25°C

0.6

125°C

60

0.4

0.2

40

20

0

5

10

15

20

25

30

35

40

0.5

1.0

1.5

2.0

2.5

3.0

V , INPUT VOLTAGE (V)

in

SWITCH CURRENT (A)

Figure 8. Standby Quiescent Current

Figure 9. Switch Saturation Voltage

8.0

6.0

4.0

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

Adjustable Version Only

V

= 12 V

Normalized at

in

25°C

2.0

0

−2.0

V

' 1.23 V

= 500 mA

−4.0

−6.0

−8.0

−10

out

I

Load

0

−50

−25

0

25

50

75

100

125

−25

0

25

50

75

100

125

T , JUNCTION TEMPERATURE (°C)

J

T , JUNCTION TEMPERATURE (°C)

J

Figure 10. Oscillator Frequency

Figure 11. Minimum Operating Voltage

100

80

Adjustable Version Only

60

40

20

0

−20

−40

−60

−80

−100

−50

−25

0

25

50

75

100

125

T , JUNCTION TEMPERATURE (°C)

J

Figure 12. Feedback Pin Current

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6

LM2576

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)

50 V

0

A

B

100 mV

Output

0

4.0 A

Voltage

Change

2.0 A

0

− 100 mV

3.0 A

4.0 A

2.0 A

0

C

D

Load

2.0 A

Current

1.0 A

0

5 ms/DIV

100 ms/DIV

Figure 13. Switching Waveforms

Figure 14. Load Transient Response

Vout = 15 V

A: Output Pin Voltage, 10 V/DIV

B: Inductor Current, 2.0 A/DIV

C: Inductor Current, 2.0 A/DIV, AC−Coupled

D: Output Ripple Voltage, 50 mV/dDIV, AC−Coupled

Horizontal Time Base: 5.0 ms/DIV

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7

LM2576

Fixed Output Voltage Versions

Feedback

4

V

in

LM2576

L1

100 mH

Fixed Output

1

V

out

Output

2

3

GN

D

5

ON/OFF

7.0 V − 40 V

Unregulated

DC Input

C

100 mF

in

C

out

1000 mF

D1

MBR360

Load

C

D1

L1

R1

R2

−

100 mF, 75 V, Aluminium Electrolytic

1000 mF, 25 V, Aluminium Electrolytic

Schottky, MBR360

100 mH, Pulse Eng. PE−92108

2.0 k, 0.1%

in

out

6.12 k, 0.1%

Adjustable Output Voltage Versions

Feedback

4

V

in

LM2576

L1

100 mH

V

out

5,000 V

Adjustable

1

Output

2

ON/OFF

3

GN

D

5

7.0 V − 40 V

Unregulated

DC Input

R2

C

100 mF

in

C

out

1000 mF

D1

MBR360

Load

R1

R2

Ǔ

R1

ǒ_{1.0 )ꢀ}

V

+ V

out

refꢀ

V

out

R2 + R1

ǒ

ꢀ–ꢀ1.0

Ǔ

V

ref

Where V = 1.23 V, R1

ref

between 1.0 k and 5.0 k

Figure 15. Typical Test Circuit

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 15, 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.

On the other hand, the PCB area connected to the Pin 2

(emitter of the internal switch) of the LM2576 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

LM2576 regulator.

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8

LM2576

PIN FUNCTION DESCRIPTION

Symbol

Description (Refer to Figure 1)

1

V

in

This pin is the positive input supply for the LM2576 step−down switching regulator. In order to minimize voltage

transients and to supply the switching currents needed by the regulator, a suitable input bypass capacitor must be

present (C in Figure 1).

in

2

Output

This is the emitter of the internal switch. The saturation voltage V of this output switch is typically 1.5 V. It should

sat

be kept in mind that the PCB area connected to this pin should be kept to a minimum in order to minimize coupling

to sensitive circuitry.

3

4

GND

Circuit ground pin. See the information about the printed circuit board layout.

Feedback

This pin senses regulated output voltage to complete the feedback loop. The signal is divided by the internal resistor

divider network R2, R1 and applied to the non−inverting input of the internal error amplifier. In the Adjustable version

of the LM2576 switching regulator this pin is the direct input of the error amplifier and the resistor network R2, R1 is

connected externally to allow programming of the output voltage.

5

ON/OFF

It allows the switching regulator circuit to be shut down using logic level signals, thus dropping the total input supply

current to approximately 80 mA. The threshold voltage is typically 1.4 V. Applying a voltage above this value (up to

+V ) shuts the regulator off. If the voltage applied to this pin is lower than 1.4 V or if this pin is left open, the

in

regulator will be in the “on” condition.

DESIGN PROCEDURE

Buck Converter Basics

This period ends when the power switch is once again

turned on. Regulation of the converter is accomplished by

varying the duty cycle of the power switch. It is possible to

describe the duty cycle as follows:

The LM2576 is a “Buck” or Step−Down Converter which

is the most elementary forward−mode converter. Its basic

schematic can be seen in Figure 16.

The operation of this regulator topology has two distinct

time periods. The first one occurs when the series switch is

on, the input voltage is connected to the input of the inductor.

The output of the inductor is the output voltage, and the

rectifier (or catch diode) is reverse biased. During this

period, since there is a constant voltage source connected

across the inductor, the inductor current begins to linearly

ramp upwards, as described by the following equation:

t

on

T

d +

, where T is the period of switching.

For the buck converter with ideal components, the duty

cycle can also be described as:

V

out

d +

V

in

Figure 17 shows the buck converter, idealized waveforms

of the catch diode voltage and the inductor current.

ǒ_{Vin out}Ǔ _ton

– V

I

+

L(on)

L

V

on(SW)

During this “on” period, energy is stored within the core

material in the form of magnetic flux. If the inductor is

properly designed, there is sufficient energy stored to carry

the requirements of the load during the “off” period.

Power

Switch

Power

Switch

Off

Power

Switch

On

Power

Switch

Off

Power

Switch

On

L

V (FWD)

D

C

V

in

D

out

R

Load

Time

Figure 16. Basic Buck Converter

I

pk

The next period is the “off” period of the power switch.

When the power switch turns off, the voltage across the

inductor reverses its polarity and is clamped at one diode

voltage drop below ground by the catch diode. The current

now flows through the catch diode thus maintaining the load

current loop. This removes the stored energy from the

inductor. The inductor current during this time is:

I

(AV)

Load

I

min

Power

Switch

Power

Switch

Diode

Time

Figure 17. Buck Converter Idealized Waveforms

ǒ_{Vout D}Ǔ _toff

– V

I

+

L(off)

L

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9

LM2576

Procedure (Fixed Output Voltage Version) In order to simplify the switching regulator design, a step−by−step

design procedure and some examples are provided.

Procedure

Example

Given Parameters:

= Regulated Output Voltage (3.3 V, 5.0 V, 12 V or 15 V)

Given Parameters:

= 5.0 V

V

out

V

out

V

= Maximum Input Voltage

V

= 15 V

in(max)

I

= Maximum Load Current

I

= 3.0 A

Load(max)

1. Controller IC Selection

According to the required input voltage, output voltage and

current, select the appropriate type of the controller IC output

voltage version.

According to the required input voltage, output voltage,

current polarity and current value, use the LM2576−5

controller IC

2. Input Capacitor Selection (C )

in

To prevent large voltage transients from appearing at the input

and for stable operation of the converter, an aluminium or

tantalum electrolytic bypass capacitor is needed between the

A 100 mF, 25 V aluminium electrolytic capacitor located near

to the input and ground pins provides sufficient bypassing.

input pin +V and ground pin GND. This capacitor should be

in

located close to the IC using short leads. This capacitor should

have a low ESR (Equivalent Series Resistance) value.

3. Catch Diode Selection (D1)

A. Since the diode maximum peak current exceeds the

regulator maximum load current the catch diode current

rating must be at least 1.2 times greater than the maximum

load current. For a robust design the diode should have a

current rating equal to the maximum current limit of the

LM2576 to be able to withstand a continuous output short

B. The reverse voltage rating of the diode should be at least

1.25 times the maximum input voltage.

A. For this example the current rating of the diode is 3.0 A.

B. Use a 20 V 1N5820 Schottky diode, or any of the

suggested fast recovery diodes shown in Table 1.

4. Inductor Selection (L1)

A. According to the required working conditions, select the

correct inductor value using the selection guide from

Figures 18 to 22.

A. Use the inductor selection guide shown in Figures 19.

B. From the appropriate inductor selection guide, identify the

inductance region intersected by the Maximum Input

Voltage line and the Maximum Load Current line. Each

region is identified by an inductance value and an inductor

code.

B. From the selection guide, the inductance area intersected

by the 15 V line and 3.0 A line is L100.

C. Select an appropriate inductor from the several different

manufacturers part numbers listed in Table 2.

The designer must realize that the inductor current rating

must be higher than the maximum peak current flowing

through the inductor. This maximum peak current can be

calculated as follows:

C. Inductor value required is 100 mH. From Table 2, choose

an inductor from any of the listed manufacturers.

ǒ_{Vin out}Ǔ _ton

–V

p(max) ^{+ I}

I

)

Load(max)

2L

where t is the “on” time of the power switch and

on

V

out

1.0

t

+

x

on

V

f

osc

in

For additional information about the inductor, see the

inductor section in the “Application Hints” section of

this data sheet.

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10

LM2576

Procedure (Fixed Output Voltage Version) (continued)In order to simplify the switching regulator design, a step−by−step

design procedure and some examples are provided.

Procedure

Example

5. Output Capacitor Selection (C )

out

5. Output Capacitor Selection (C

)

out

A. Since the LM2576 is a forward−mode switching regulator

A. C = 680 mF to 2000 mF standard aluminium electrolytic.

out

with voltage mode control, its open loop 2−pole−1−zero

frequency characteristic has the dominant pole−pair

determined by the output capacitor and inductor values. For

stable operation and an acceptable ripple voltage,

(approximately 1% of the output voltage) a value between

680 mF and 2000 mF is recommended.

B. Due to the fact that the higher voltage electrolytic capacitors

generally have lower ESR (Equivalent Series Resistance)

numbers, the output capacitor’s voltage rating should be at

least 1.5 times greater than the output voltage. For a 5.0 V

regulator, a rating at least 8.0 V is appropriate, and a 10 V or

16 V rating is recommended.

B. Capacitor voltage rating = 20 V.

Procedure (Adjustable Output Version: LM2576−ADJ)

Procedure

Example

Given Parameters:

V

out

= Regulated Output Voltage

V

out

= 8.0 V

V

= Maximum DC Input Voltage

V

= 25 V

in(max)

I

= Maximum Load Current

I

= 2.5 A

Load(max)

1. Programming Output Voltage

1. Programming Output Voltage (selecting R1 and R2)

To select the right programming resistor R1 and R2 value (see

Figure 2) use the following formula:

Select R1 and R2:

R2

R1

_{+ 1.23}ǒ_{1.0 )}

Ǔ

V

Select R1 = 1.8 kW

out

R2

R1

_refǒ_{1.0 )}

Ǔ

V

+ V

where V = 1.23 V

ref

out

V

out

8.0 V

_{+ 1.8 k}ǒ

_{* 1.0}Ǔ

1.23 V

_{R2 + R1}ǒ Ǔ

* 1.0

Resistor R1 can be between 1.0 k and 5.0 kW. (For best

temperature coefficient and stability with time, use 1% metal

film resistors).

V

ref

R2 = 9.91 kW, choose a 9.88 k metal film resistor.

V

out

_{R2 + R1}ǒ Ǔ

– 1.0

V

ref

2. Input Capacitor Selection (C )

in

To prevent large voltage transients from appearing at the input

and for stable operation of the converter, an aluminium or

tantalum electrolytic bypass capacitor is needed between the

A 100 mF, 150 V aluminium electrolytic capacitor located near

the input and ground pin provides sufficient bypassing.

input pin +V and ground pin GND This capacitor should be

in

located close to the IC using short leads. This capacitor should

have a low ESR (Equivalent Series Resistance) value.

For additional information see input capacitor section in the

“Application Hints” section of this data sheet.

3. Catch Diode Selection (D1)

A. Since the diode maximum peak current exceeds the

regulator maximum load current the catch diode current

rating must be at least 1.2 times greater than the maximum

load current. For a robust design, the diode should have a

current rating equal to the maximum current limit of the

LM2576 to be able to withstand a continuous output short.

B. The reverse voltage rating of the diode should be at least

1.25 times the maximum input voltage.

A. For this example, a 3.0 A current rating is adequate.

B. Use a 30 V 1N5821 Schottky diode or any suggested fast

recovery diode in the Table 1.

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LM2576

Procedure (Adjustable Output Version: LM2576−ADJ) (continued)

Procedure

Example

A. Calculate E x T [V x ms] constant:

8.0 1000

4. Inductor Selection (L1)

A. Use the following formula to calculate the inductor Volt x

microsecond [V x ms] constant:

_{E x T +}ǒ_{Vin out}Ǔ ^Vout

E x T + 25 – 8.0 x

x

+ 80 [V x ms]

6

10

(

)

– V

x

[V x ms]

25

52

V

F[Hz]

in

B. Match the calculated E x T value with the corresponding

number on the vertical axis of the Inductor Value Selection

Guide shown in Figure 22. This E x T constant is a

measure of the energy handling capability of an inductor and

is dependent upon the type of core, the core area, the

number of turns, and the duty cycle.

B. E x T = 80 [V x ms]

C. Next step is to identify the inductance region intersected by

the E x T value and the maximum load current value on the

horizontal axis shown in Figure 25.

C. I

= 2.5 A

Load(max)

Inductance Region = H150

D. From the inductor code, identify the inductor value. Then

select an appropriate inductor from Table 2.

D. Proper inductor value = 150 mH

Choose the inductor from Table 2.

The inductor chosen must be rated for a switching

frequency of 52 kHz and for a current rating of 1.15 x I

The inductor current rating can also be determined by

calculating the inductor peak current:

.

Load

ǒ_{Vin out}Ǔ_ton

– V

p(max) ^{+ I}

I

)

Load(max)

2L

where t is the “on” time of the power switch and

on

V

out

1.0

t

+

x

on

V

f

osc

in

For additional information about the inductor, see the

inductor section in the “External Components” section of

this data sheet.

5. Output Capacitor Selection (C

)

out

5. Output Capacitor Selection (C

)

out

A. Since the LM2576 is a forward−mode switching regulator

with voltage mode control, its open loop 2−pole−1−zero

frequency characteristic has the dominant pole−pair

determined by the output capacitor and inductor values.

A.

25

8 x 150

C

w 13,300 x

+ 332.5 μF

out

To achieve an acceptable ripple voltage, select

C

out

= 680 mF electrolytic capacitor.

For stable operation, the capacitor must satisfy the

following requirement:

V

in(max)

C

w 13,300

[μF]

out

V

x L [μH]

out

B. Capacitor values between 10 mF and 2000 mF will satisfy

the loop requirements for stable operation. To achieve an

acceptable output ripple voltage and transient response, the

output capacitor may need to be several times larger than

the above formula yields.

C. Due to the fact that the higher voltage electrolytic capacitors

generally have lower ESR (Equivalent Series Resistance)

numbers, the output capacitor’s voltage rating should be at

least 1.5 times greater than the output voltage. For a 5.0 V

regulator, a rating of at least 8.0 V is appropriate, and a 10 V

or 16 V rating is recommended.

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12

LM2576

LM2576 Series Buck Regulator Design Procedures (continued)

Indicator Value Selection Guide (For Continuous Mode Operation)

60

L680

40

20

15

H1000

H680

H470

L330

H330

H220

H150

L470

40

L330

20

15

L680

10

L220

L470

8.0

12

L150

7.0

L220

10

L100

L150

L68

9.0

6.0

L100

8.0

L47

L68

L47

5.0

0.3

7.0

0.3

0.4 0.5 0.6

0.8 1.0

1.5

2.0 2.5 3.0

0.4 0.5 0.6

0.8 1.0 1.2 1.5

2.0

2.5 3.0

I , MAXIMUM LOAD CURRENT (A)

L

I , MAXIMUM LOAD CURRENT (A)

L

Figure 18. LM2576−3.3

Figure 19. LM2576−5

60

40

35

30

40

35

30

H1500

25

H1000

L470

H1000

H680

H470

25

H680

H470

H330

20

18

H220

H150

H330

H220

22

H150

20

19

L680

L470

16

15

L330

L220

L150

18

L100

L68

14

0.3

17

0.3

0.4 0.5 0.6

0.8 1.0

1.5

2.0 2.5 3.0

0.4 0.5 0.6

0.8 1.0

1.5

2.0 2.5 3.0

I , MAXIMUM LOAD CURRENT (A)

L

I , MAXIMUM LOAD CURRENT (A)

L

Figure 20. LM2576−12

Figure 21. LM2576−15

300

250

H2000

200

150

H1500

H1000

H680

L220

H470

L150

H330

H220

100

90

H150

80

70

L680

60

50

45

40

L470

L330

L100

1.5

35

L68

30

L47

25

20

0.3

0.4 0.5 0.6

0.8 1.0

2.0 2.5 3.0

I , MAXIMUM LOAD CURRENT (A)

L

Figure 22. LM2576−ADJ

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13

LM2576

Table 1. Diode Selection Guide

Schottky

Fast Recovery

3.0 A

4.0 − 6.0 A

Through Surface

3.0 A

4.0 − 6.0 A

Through

Hole

Surface

Mount

Through

Hole

Surface

Mount

Through

Surface

Mount

Hole

Mount

Hole

V

R

20 V

1N5820

MBR320P

SR302

SK32

1N5823

SR502

SB520

30 V

1N5821

MBR330

SR303

SK33

30WQ03

1N5824

SR503

SB530

50WQ03

MUR320

31DF1

HER302

MURS320T3

MURD320

30WF10

MUR420

HER602

MURD620CT

50WF10

31DQ03

40 V

1N5822

MBR340

SR304

SK34

30WQ04

MBRS340T3

MBRD340

1N5825

SR504

SB540

MBRD640CT

50WQ04

(all diodes

rated

(all diodes

rated

(all diodes

rated

(all diodes

rated

31DQ04

to at least

100 V)

to at least

100 V)

to at least

100 V)

to at least

100 V)

50 V

60 V

MBR350

31DQ05

SR305

SK35

30WQ05

SB550

50WQ05

MBR360

DQ06

MBRS360T3

MBRD360

50SQ080

MBRD660CT

SR306

NOTE: Diodes listed in bold are available from ON Semiconductor.

Table 2. Inductor Selection by Manufacturer’s Part Number

Inductor

Code

Inductor

Value

Tech 39

Schott Corp.

Pulse Eng.

Renco

L47

L68

47 mH

68 mH

77 212

671 26980

PE−53112

PE−92114

PE−92108

PE−53113

PE−52626

PE−52627

PE−53114

PE−52629

PE−53115

PE−53116

PE−53117

PE−53118

PE−53119

PE−53120

PE−53121

PE−53122

RL2442

77 262

77 312

77 360

77 408

77 456

*

671 26990

671 27000

671 27010

671 27020

671 27030

671 27040

671 27050

671 27060

671 27070

671 27080

671 27090

671 27100

671 27110

671 27120

671 27130

RL2443

RL2444

RL1954

RL1953

RL1952

RL1951

RL1950

RL2445

RL2446

RL2447

RL1961

RL1960

RL1959

RL1958

RL2448

L100

L150

L220

L330

L470

L680

H150

H220

H330

H470

H680

H1000

H1500

100 mH

150 mH

220 mH

330 mH

470 mH

680 mH

150 mH

220 mH

330 mH

470 mH

680 mH

1000 mH

1500 mH

2200 mH

77 506

77 362

77 412

77 462

*

77 508

77 556

*

H2200

*

NOTE: *Contact Manufacturer

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14

LM2576

Table 3. Example of Several Inductor Manufacturers Phone/Fax Numbers

Phone

Fax

+ 1−619−674−8100

+ 1−619−674−8262

Pulse Engineering, Inc.

Pulse Engineering, Inc. Europe

Renco Electronics, Inc.

Tech 39

Phone

Fax

+ 353−9324−107

+ 353−9324−459

Phone

Fax

+ 1−516−645−5828

+ 1−516−586−5562

Phone

Fax

+ 33−1−4115−1681

+ 33−1−4709−5051

Phone

Fax

+ 1−612−475−1173

+ 1−612−475−1786

Schott Corporation

EXTERNAL COMPONENTS

Input Capacitor (C_in)

Output Capacitor (C_out

)

The Input Capacitor Should Have a Low ESR

For low output ripple voltage and good stability, low ESR

output capacitors are recommended. An output capacitor

has two main functions: it filters the output and provides

regulator loop stability. The ESR of the output capacitor and

the peak−to−peak value of the inductor ripple current are the

main factors contributing to the output ripple voltage value.

Standard aluminium electrolytics could be adequate for

some applications but for quality design, low ESR types are

recommended.

An aluminium electrolytic capacitor’s ESR value is

related to many factors such as the capacitance value, the

voltage rating, the physical size and the type of construction.

In most cases, the higher voltage electrolytic capacitors have

lower ESR value. Often capacitors with much higher

voltage ratings may be needed to provide low ESR values

that, are required for low output ripple voltage.

For stable operation of the switch mode converter a low

ESR (Equivalent Series Resistance) aluminium or solid

tantalum bypass capacitor is needed between the input pin

and the ground pin, to prevent large voltage transients from

appearing at the input. It must be located near the regulator

and use short leads. With most electrolytic capacitors, the

capacitance value decreases and the ESR increases with

lower temperatures. For reliable operation in temperatures

below −25°C larger values of the input capacitor may be

needed. Also paralleling a ceramic or solid tantalum

capacitor will increase the regulator stability at cold

temperatures.

RMS Current Rating of C

in

The important parameter of the input capacitor is the RMS

current rating. Capacitors that are physically large and have

large surface area will typically have higher RMS current

ratings. For a given capacitor value, a higher voltage

electrolytic capacitor will be physically larger than a lower

voltage capacitor, and thus be able to dissipate more heat to

the surrounding air, and therefore will have a higher RMS

current rating. The consequence of operating an electrolytic

capacitor beyond the RMS current rating is a shortened

operating life. In order to assure maximum capacitor

operating lifetime, the capacitor’s RMS ripple current rating

should be:

The Output Capacitor Requires an ESR Value

That Has an Upper and Lower Limit

As mentioned above, a low ESR value is needed for low

output ripple voltage, typically 1% to 2% of the output

voltage. But if the selected capacitor’s ESR is extremely low

(below 0.05 W), there is a possibility of an unstable feedback

loop, resulting in oscillation at the output. This situation can

occur when a tantalum capacitor, that can have a very low

ESR, is used as the only output capacitor.

At Low Temperatures, Put in Parallel Aluminium

Electrolytic Capacitors with Tantalum Capacitors

Electrolytic capacitors are not recommended for

temperatures below −25°C. The ESR rises dramatically at

cold temperatures and typically rises 3 times at −25°C and

as much as 10 times at −40°C. Solid tantalum capacitors

have much better ESR spec at cold temperatures and are

recommended for temperatures below −25°C. They can be

also used in parallel with aluminium electrolytics. The value

of the tantalum capacitor should be about 10% or 20% of the

total capacitance. The output capacitor should have at least

50% higher RMS ripple current rating at 52 kHz than the

peak−to−peak inductor ripple current.

I_rms> 1.2 x d x I_Load

where d is the duty cycle, for a buck regulator

V

t

on

T

out

d +

|V

+

V

in

|

t

on

T

out

|V | ) V

and d +

+

for a buck*boost regulator.

out

in

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15

LM2576

Catch Diode

ripple voltage. On the other hand it does require larger

Locate the Catch Diode Close to the LM2576

The LM2576 is a step−down buck converter; it requires a

fast diode to provide a return path for the inductor current

when the switch turns off. This diode must be located close

to the LM2576 using short leads and short printed circuit

traces to avoid EMI problems.

inductor values to keep the inductor current flowing

continuously, especially at low output load currents and/or

high input voltages.

To simplify the inductor selection process, an inductor

selection guide for the LM2576 regulator was added to this

data sheet (Figures 18 through 22). This guide assumes that

the regulator is operating in the continuous mode, and

selects an inductor that will allow a peak−to−peak inductor

ripple current to be a certain percentage of the maximum

design load current. This percentage is allowed to change as

different design load currents are selected. For light loads

(less than approximately 300 mA) it may be desirable to

operate the regulator in the discontinuous mode, because the

inductor value and size can be kept relatively low.

Consequently, the percentage of inductor peak−to−peak

current increases. This discontinuous mode of operation is

perfectly acceptable for this type of switching converter.

Any buck regulator will be forced to enter discontinuous

mode if the load current is light enough.

Use a Schottky or a Soft Switching

Ultra−Fast Recovery Diode

Since the rectifier diodes are very significant sources of

losses within switching power supplies, choosing the

rectifier that best fits into the converter design is an

important process. Schottky diodes provide the best

performance because of their fast switching speed and low

forward voltage drop.

They provide the best efficiency especially in low output

voltage applications (5.0 V and lower). Another choice

could be Fast−Recovery, or Ultra−Fast Recovery diodes. It

has to be noted, that some types of these diodes with an

abrupt turnoff characteristic may cause instability or

EMI troubles.

A fast−recovery diode with soft recovery characteristics

can better fulfill some quality, low noise design requirements.

Table 1 provides a list of suitable diodes for the LM2576

regulator. Standard 50/60 Hz rectifier diodes, such as the

1N4001 series or 1N5400 series are NOT suitable.

2.0 A

Inductor

Current

Waveform

0 A

Inductor

2.0 A

Power

Switch

The magnetic components are the cornerstone of all

switching power supply designs. The style of the core and

the winding technique used in the magnetic component’s

design has a great influence on the reliability of the overall

power supply.

Current

Waveform

0 A

Using an improper or poorly designed inductor can cause

high voltage spikes generated by the rate of transitions in

current within the switching power supply, and the

possibility of core saturation can arise during an abnormal

operational mode. Voltage spikes can cause the

semiconductors to enter avalanche breakdown and the part

can instantly fail if enough energy is applied. It can also

cause significant RFI (Radio Frequency Interference) and

EMI (Electro−Magnetic Interference) problems.

HORIZONTAL TIME BASE: 5.0 ms/DIV

Figure 23. Continuous Mode Switching Current

Waveforms

Selecting the Right Inductor Style

Some important considerations when selecting a core type

are core material, cost, the output power of the power supply,

the physical volume the inductor must fit within, and the

amount of EMI (Electro−Magnetic Interference) shielding

that the core must provide. The inductor selection guide

covers different styles of inductors, such as pot core, E−core,

toroid and bobbin core, as well as different core materials

such as ferrites and powdered iron from different

manufacturers.

For high quality design regulators the toroid core seems to

be the best choice. Since the magnetic flux is contained

within the core, it generates less EMI, reducing noise

problems in sensitive circuits. The least expensive is the

bobbin core type, which consists of wire wound on a ferrite

rod core. This type of inductor generates more EMI due to

the fact that its core is open, and the magnetic flux is not

contained within the core.

Continuous and Discontinuous Mode of Operation

The LM2576 step−down converter can operate in both the

continuous and the discontinuous modes of operation. The

regulator works in the continuous mode when loads are

relatively heavy, the current flows through the inductor

continuously and never falls to zero. Under light load

conditions, the circuit will be forced to the discontinuous

mode when inductor current falls to zero for certain period

of time (see Figure 23 and Figure 24). Each mode has

distinctively different operating characteristics, which can

affect the regulator performance and requirements. In many

cases the preferred mode of operation is the continuous

mode. It offers greater output power, lower peak currents in

the switch, inductor and diode, and can have a lower output

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LM2576

When multiple switching regulators are located on the

inductor and/or the LM2576. Different inductor types have

different saturation characteristics, and this should be kept

in mind when selecting an inductor.

same printed circuit board, open core magnetics can cause

interference between two or more of the regulator circuits,

especially at high currents due to mutual coupling. A toroid,

pot core or E−core (closed magnetic structure) should be

used in such applications.

Do Not Operate an Inductor Beyond its

Maximum Rated Current

0.4 A

Inductor

Current

Waveform

0 A

Exceeding an inductor’s maximum current rating may

cause the inductor to overheat because of the copper wire

losses, or the core may saturate. Core saturation occurs when

the flux density is too high and consequently the cross

sectional area of the core can no longer support additional

lines of magnetic flux.

This causes the permeability of the core to drop, the

inductance value decreases rapidly and the inductor begins

to look mainly resistive. It has only the DC resistance of the

winding. This can cause the switch current to rise very

rapidly and force the LM2576 internal switch into

cycle−by−cycle current limit, thus reducing the DC output

load current. This can also result in overheating of the

0.4 A

Power

Switch

Current

Waveform

0 A

HORIZONTAL TIME BASE: 5.0 ms/DIV

Figure 24. Discontinuous Mode Switching Current

Waveforms

GENERAL RECOMMENDATIONS

Output Voltage Ripple and Transients

Minimizing the Output Ripple

Source of the Output Ripple

In order to minimize the output ripple voltage it is possible

to enlarge the inductance value of the inductor L1 and/or to

use a larger value output capacitor. There is also another way

to smooth the output by means of an additional LC filter (20

mH, 100 mF), that can be added to the output (see Figure 34)

to further reduce the amount of output ripple and transients.

With such a filter it is possible to reduce the output ripple

voltage transients 10 times or more. Figure 25 shows the

difference between filtered and unfiltered output waveforms

of the regulator shown in Figure 34.

Since the LM2576 is a switch mode power supply

regulator, its output voltage, if left unfiltered, will contain a

sawtooth ripple voltage at the switching frequency. The

output ripple voltage value ranges from 0.5% to 3% of the

output voltage. It is caused mainly by the inductor sawtooth

ripple current multiplied by the ESR of the output capacitor.

Short Voltage Spikes and How to Reduce Them

The regulator output voltage may also contain short

voltage spikes at the peaks of the sawtooth waveform (see

Figure 25). These voltage spikes are present because of the

fast switching action of the output switch, and the parasitic

inductance of the output filter capacitor. There are some

other important factors such as wiring inductance, stray

capacitance, as well as the scope probe used to evaluate these

transients, all these contribute to the amplitude of these

spikes. To minimize these voltage spikes, low inductance

capacitors should be used, and their lead lengths must be

kept short. The importance of quality printed circuit board

layout design should also be highlighted.

The lower waveform is from the normal unfiltered output

of the converter, while the upper waveform shows the output

ripple voltage filtered by an additional LC filter.

Heatsinking and Thermal Considerations

The Through−Hole Package TO−220

The LM2576 is available in two packages, a 5−pin

2

TO−220(T, TV) and a 5−pin surface mount D PAK(D2T).

Although the TO−220(T) package needs a heatsink under

most conditions, there are some applications that require no

heatsink to keep the LM2576 junction temperature within

the allowed operating range. Higher ambient temperatures

require some heat sinking, either to the printed circuit (PC)

board or an external heatsink.

Voltage spikes

caused by

switching action

of the output

switch and the

parasitic

inductance of the

output capacitor

Filtered

Output

Voltage

The Surface Mount Package D²PAK and its

Heatsinking

The other type of package, the surface mount D PAK, is

2

designed to be soldered to the copper on the PC board. The

copper and the board are the heatsink for this package and

the other heat producing components, such as the catch

diode and inductor. The PC board copper area that the

Unfiltered

Output

Voltage

2

package is soldered to should be at least 0.4 in (or 260 mm )

HORIZONTAL TIME BASE: 5.0 ms/DIV

2

and ideally should have 2 or more square inches (1300 mm )

Figure 25. Output Ripple Voltage Waveforms

of 0.0028 inch copper. Additional increases of copper area

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LM2576

2

Packages on a Heatsink

beyond approximately 6.0 in (4000 mm ) will not improve

heat dissipation significantly. If further thermal

improvements are needed, double sided or multilayer PC

boards with large copper areas should be considered. In

order to achieve the best thermal performance, it is highly

recommended to use wide copper traces as well as large

areas of copper in the printed circuit board layout. The only

exception to this is the OUTPUT (switch) pin, which should

not have large areas of copper (see page 8 ‘PCB Layout

Guideline’).

If the actual operating junction temperature is greater than

the selected safe operating junction temperature determined

in step 3, than a heatsink is required. The junction

temperature will be calculated as follows:

T_J= P_D(R_q+ R_q+ R_q_SA) + T_A

JA

CS

where

R

qJC

R

qCS

R

qSA

is the thermal resistance junction−case,

is the thermal resistance case−heatsink,

is the thermal resistance heatsink−ambient.

If the actual operating temperature is greater than the

selected safe operating junction temperature, then a larger

heatsink is required.

Thermal Analysis and Design

The following procedure must be performed to determine

whether or not a heatsink will be required. First determine:

Some Aspects That can Influence Thermal Design

It should be noted that the package thermal resistance and

the junction temperature rise numbers are all approximate,

and there are many factors that will affect these numbers,

such as PC board size, shape, thickness, physical position,

location, board temperature, as well as whether the

surrounding air is moving or still.

Other factors are trace width, total printed circuit copper

area, copper thickness, single− or double−sided, multilayer

board, the amount of solder on the board or even color of the

traces.

1. P

2. T

3. T

maximum regulator power dissipation in the

application.

maximum ambient temperature in the

application.

maximum allowed junction temperature

(125°C for the LM2576). For a conservative

design, the maximum junction temperature

should not exceed 110°C to assure safe

operation. For every additional +10°C

temperature rise that the junction must

withstand, the estimated operating lifetime

of the component is halved.

D(max)

)

A(max

J(max)

The size, quantity and spacing of other components on the

board can also influence its effectiveness to dissipate the heat.

4. R

5. R

package thermal resistance junction−case.

package thermal resistance junction−ambient.

qJC

qJA

12 to 40 V

Feedback

Unregulated

(Refer to Maximum Ratings on page 2 of this data sheet or

and R values).

DC Input

L1

68 mH

+V

4

in

R

qJC

qJA

LM2576−12

Output

1

The following formula is to calculate the approximate

total power dissipated by the LM2576:

C

100 mF

in

2

ON/OFF

D1

1N5822

C

out

2200 mF

3

GN

D

5

P_D= (V_inx I_Q) + d x I_Loadx V_sat

where d is the duty cycle and for buck converter

−12 V @ 0.7 A

Regulated

Output

V

t

on

T

O

in

d +

+

,

Figure 26. Inverting Buck−Boost Develops −12 V

ADDITIONAL APPLICATIONS

I

(quiescent current) and V can be found in the

Q

sat

LM2576 data sheet,

V

is minimum input voltage applied,

is the regulator output voltage,

is the load current.

in

Inverting Regulator

V

O

An inverting buck−boost regulator using the LM2576−12

is shown in Figure 26. This circuit converts a positive input

voltage to a negative output voltage with a common ground

by bootstrapping the regulators ground to the negative

output voltage. By grounding the feedback pin, the regulator

senses the inverted output voltage and regulates it.

In this example the LM2576−12 is used to generate a

−12 V output. The maximum input voltage in this case

cannot exceed +28 V because the maximum voltage

appearing across the regulator is the absolute sum of the

input and output voltages and this must be limited to a

maximum of 40 V.

I

Load

The dynamic switching losses during turn−on and

turn−off can be neglected if proper type catch diode is used.

Packages Not on a Heatsink (Free−Standing)

For a free−standing application when no heatsink is used,

the junction temperature can be determined by the following

expression:

T_J= (R_q_JA) (P_D) + T_A

where (R )(P ) represents the junction temperature rise

qJA

D

caused by the dissipated power and T is the maximum

A

ambient temperature.

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18

LM2576

This circuit configuration is able to deliver approximately

I

(V ) |V |)

Load in

V

x t

on

O

in

2L

I

[

)

0.7 A to the output when the input voltage is 12 V or higher.

At lighter loads the minimum input voltage required drops

to approximately 4.7 V, because the buck−boost regulator

topology can produce an output voltage that, in its absolute

value, is either greater or less than the input voltage.

Since the switch currents in this buck−boost configuration

are higher than in the standard buck converter topology, the

available output current is lower.

This type of buck−boost inverting regulator can also

require a larger amount of startup input current, even for

light loads. This may overload an input power source with

a current limit less than 5.0 A.

Such an amount of input startup current is needed for at

least 2.0 ms or more. The actual time depends on the output

voltage and size of the output capacitor.

Because of the relatively high startup currents required by

this inverting regulator topology, the use of a delayed startup

or an undervoltage lockout circuit is recommended.

Using a delayed startup arrangement, the input capacitor

can charge up to a higher voltage before the switch−mode

regulator begins to operate.

peak

V

in

x

1

|V |

O

1.0

where t

+

, and f

+ 52 kHz.

osc

on

V

) |V |

f

osc

in

O

Under normal continuous inductor current operating

conditions, the worst case occurs when V is minimal.

in

12 V to 25 V

Unregulated

DC Input

Feedback

4

Output

+V

in

L1

68 mH

LM2576−12

1

C

100 mF

/50 V

in

C1

0.1 mF

2

5

ON/OFF 3 GN

D

C

out

2200 mF

/16 V

D1

1N5822

R1

47 k

R2

47 k

−12 V @ 700 m A

Regulated

Output

Figure 27. Inverting Buck−Boost Regulator

with Delayed startup

The high input current needed for startup is now partially

supplied by the input capacitor C .

in

It has been already mentioned above, that in some

situations, the delayed startup or the undervoltage lockout

features could be very useful. A delayed startup circuit

applied to a buck−boost converter is shown in Figure 27,

Figure 33 in the “Undervoltage Lockout” section describes

an undervoltage lockout feature for the same converter

topology.

+V

in

LM2576−XX

1

C

R1

100 mF 47 k

in

5

ON/OFF 3 GN

D

Shutdown

Input

5.0 V

Off

R3

470

0

On

Design Recommendations:

R2

47 k

The inverting regulator operates in a different manner

than the buck converter and so a different design procedure

has to be used to select the inductor L1 or the output

−V

out

MOC8101

capacitor C

.

out

The output capacitor values must be larger than what is

normally required for buck converter designs. Low input

voltages or high output currents require a large value output

capacitor (in the range of thousands of mF).

NOTE: This picture does not show the complete circuit.

Figure 28. Inverting Buck−Boost Regulator Shutdown

Circuit Using an Optocoupler

The recommended range of inductor values for the

inverting converter design is between 68 mH and 220 mH. To

select an inductor with an appropriate current rating, the

inductor peak current has to be calculated.

The following formula is used to obtain the peak inductor

current:

With the inverting configuration, the use of the ON/OFF

pin requires some level shifting techniques. This is caused

by the fact, that the ground pin of the converter IC is no

longer at ground. Now, the ON/OFF pin threshold voltage

(1.3 V approximately) has to be related to the negative

output voltage level. There are many different possible shut

down methods, two of them are shown in Figures 28 and 29.

http://onsemi.com

19

LM2576

Shutdown

Input

Another important point is that these negative boost

+V

0

Off

converters cannot provide current limiting load protection in

the event of a short in the output so some other means, such

as a fuse, may be necessary to provide the load protection.

On

R2

5.6 k

+V

in

+V

in

Delayed Startup

1

There are some applications, like the inverting regulator

already mentioned above, which require a higher amount of

startup current. In such cases, if the input power source is

limited, this delayed startup feature becomes very useful.

To provide a time delay between the time when the input

voltage is applied and the time when the output voltage

comes up, the circuit in Figure 31 can be used. As the input

voltage is applied, the capacitor C1 charges up, and the

voltage across the resistor R2 falls down. When the voltage

on the ON/OFF pin falls below the threshold value 1.3 V, the

regulator starts up. Resistor R1 is included to limit the

maximum voltage applied to the ON/OFF pin. It reduces the

power supply noise sensitivity, and also limits the capacitor

C1 discharge current, but its use is not mandatory.

When a high 50 Hz or 60 Hz (100 Hz or 120 Hz

respectively) ripple voltage exists, a long delay time can

cause some problems by coupling the ripple into the

ON/OFF pin, the regulator could be switched periodically

on and off with the line (or double) frequency.

LM2576−XX

C

100 mF

in

Q1

2N3906

5

ON/OFF 3 GN

D

R1

12 k

−V

out

NOTE: This picture does not show the complete circuit.

Figure 29. Inverting Buck−Boost Regulator Shutdown

Circuit Using a PNP Transistor

Negative Boost Regulator

This example is a variation of the buck−boost topology

and it is called negative boost regulator. This regulator

experiences relatively high switch current, especially at low

input voltages. The internal switch current limiting results in

lower output load current capability.

The circuit in Figure 30 shows the negative boost

configuration. The input voltage in this application ranges

from −5.0 V to −12 V and provides a regulated −12 V output.

If the input voltage is greater than −12 V, the output will rise

above −12 V accordingly, but will not damage the regulator.

+V

in

+V

in

LM2576−XX

1

C1

0.1 mF

5

ON/OFF 3 GN

D

C

100 mF

in

C

out

2200 mF

Low Esr

R1

47 k

4

R2

47 k

V

in

Feedback

Output

2

LM2576−12

1

C

100 mF

in

1N5820

3

5

GND

ON/OFF

NOTE: This picture does not show the complete circuit.

V

out

= −12 V

Figure 31. Delayed Startup Circuitry

Typical Load Current

400 mA for V = −5.2 V

750 mA for V = −7.0 V

100 mH

V

in

Undervoltage Lockout

in

Some applications require the regulator to remain off until

the input voltage reaches a certain threshold level. Figure 32

shows an undervoltage lockout circuit applied to a buck

regulator. A version of this circuit for buck−boost converter

is shown in Figure 33. Resistor R3 pulls the ON/OFF pin

high and keeps the regulator off until the input voltage

reaches a predetermined threshold level with respect to the

ground Pin 3, which is determined by the following

expression:

−5.0 V to −12 V

Figure 30. Negative Boost Regulator

Design Recommendations:

The same design rules as for the previous inverting

buck−boost converter can be applied. The output capacitor

C

must be chosen larger than would be required for a what

out

standard buck converter. Low input voltages or high output

currents require a large value output capacitor (in the range

of thousands of mF). The recommended range of inductor

values for the negative boost regulator is the same as for

inverting converter design.

R2

R1

₎ǒ_{1.0 )}Ǔ _VBE

Z1

( )

Q1

V

[ V

th

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20

LM2576

Under normal continuous inductor current operating

conditions, the worst case occurs when V is minimal.

in

+V

in

+V

in

LM2576−XX

1

C

100 mF

in

R2

10 k

R3

47 k

+V

in

+V

in

5

ON/OFF 3 GN

D

LM2576−XX

1

C

100 mF

in

R2

15 k

R3

47 k

Z1

1N5242B

5

ON/OFF 3 GN

D

Q1

2N3904

Z1

1N5242B

R1

10 k

V

≈ 13 V

th

V

≈ 13 V

th

Q1

2N3904

R1

15 k

NOTE: This picture does not show the complete circuit.

V

out

Figure 32. Undervoltage Lockout Circuit for

Buck Converter

NOTE: This picture does not show the complete circuit.

The following formula is used to obtain the peak inductor

current:

Figure 33. Undervoltage Lockout Circuit for

Buck−Boost Converter

I

(V ) |V |)

Load in

V

x t

on

O

in

2L

I

[

)

Adjustable Output, Low−Ripple Power Supply

peak

V

in

x

1

A 3.0 A output current capability power supply that

features an adjustable output voltage is shown in Figure 34.

This regulator delivers 3.0 A into 1.2 V to 35 V output.

The input voltage ranges from roughly 3.0 V to 40 V. In order

to achieve a 10 or more times reduction of output ripple, an

additional L−C filter is included in this circuit.

|V |

O

1.0

where t

+

, and f

+ 52 kHz.

osc

on

V

) |V |

f

osc

in

O

Feedback

40 V Max

Unregulated

DC Input

4

+V

in

L1

150 mH

L2

20 mH

LM2574−Adj

Output

Voltage

1

Output

2

ON/OFF

1.2 to 35 V @ 3.0 A

R2

50 k

C

100 mF

in

3

GN

D

5

C

out

2200 mF

D1

1N5822

C1

100 mF

R1

1.21 k

Optional Output

Ripple Filter

Figure 34. 1.2 to 35 V Adjustable 3.0 A Power Supply with Low Output Ripple

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21

LM2576

THE LM2576−5 STEP−DOWN VOLTAGE REGULATOR WITH 5.0 V @ 3.0 A OUTPUT POWER CAPABILITY.

TYPICAL APPLICATION WITH THROUGH−HOLE PC BOARD LAYOUT

Feedback

4

+V

in

Unregulated

DC Input

+V = 7.0 to 40 V

L1

150 mH

LM2576−5

1

Output

2

Regulated Output

= 5.0 V @ 3.0 A

in

V

out1

3

GN

D

5

ON/OFF

C1

100 mF

/50 V

ON/OFF

C

out

1000 mF

/16 V

D1

1N5822

GND

in

GND

out

C1

C2

D1

L1

−

100 mF, 50 V, Aluminium Electrolytic

1000 mF, 16 V, Aluminium Electrolytic

3.0 A, 40 V, Schottky Rectifier, 1N5822

150 mH, RL2444, Renco Electronics

Figure 35. Schematic Diagram of the LM2576−5 Step−Down Converter

LM2576

U1

D1

+

C2

C1

V

ou

t

+

ON/OFF

L1

+V

in

GND-

GND

out

in

NOTE: Not to scale.

Figure 36. Printed Circuit Board Layout

Component Side

Figure 37. Printed Circuit Board Layout

Copper Side

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22

LM2576

THE LM2576−ADJ STEP−DOWN VOLTAGE REGULATOR WITH 8.0 V @ 1.0 A OUTPUT POWER

CAPABILITY. TYPICAL APPLICATION WITH THROUGH−HOLE PC BOARD LAYOUT

4

Feedback

Unregulated

DC Input

+V

in

L1

150 mH

LM2576−ADJ

Regulated

Output Filtered

1

+V = 10 V to 40 V

in

Output

2

ON/OFF

V

out2

= 8.0 V @ 3.0 A

R2

10 k

3

GN

D

5

C1

100 mF

/50 V

C2

1000 mF

/16 V

D1

1N5822

R1

1.8 k

ON/OFF

R2

R1

₎ǒ_{1.0 )}

Ǔ

V

+ V

out

ref

C1

C2

D1

L1

R1

R2

−

100 mF, 50 V, Aluminium Electrolytic

1000 mF, 16 V, Aluminium Electrolytic

3.0 A, 40 V, Schottky Rectifier, 1N5822

150 mH, RL2444, Renco Electronics

1.8 kW, 0.25 W

V

ref

= 1.23 V

R1 is between 1.0 k and 5.0 k

10 kW, 0.25 W

Figure 38. Schematic Diagram of the 8.0 V @ 3.0 A Step−Down Converter Using the LM2576−ADJ

LM2576

U1

D1

R1

R2

ON/OFF

C1

+

C2

V

out

+V

in

L1

GND

out

in

NOTE: Not to scale.

Figure 39. Printed Circuit Board Layout

Component Side

Figure 40. Printed Circuit Board Layout

Copper Side

References

• National Semiconductor LM2576 Data Sheet and Application Note

• National Semiconductor LM2595 Data Sheet and Application Note

• Marty Brown “Practical Switching Power Supply Design”, Academic Press, Inc., San Diego 1990

• Ray Ridley “High Frequency Magnetics Design”, Ridley Engineering, Inc. 1995

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23

LM2576

ORDERING INFORMATION

Nominal

Output Voltage

Operating

Temperature Range

†

Device

LM2576TV−ADJ

LM2576TV−ADJG

Package

Shipping

TO−220 (Vertical Mount)

(Pb−Free)

TO−220 (Straight Lead)

LM2576T−ADJ

50 Units/Rail

2500 Tape & Reel

50 Units/Rail

TO−220 (Straight Lead)

(Pb−Free)

LM2576T−ADJG

1.23 V to 37 V

T = −40° to +125°C

J

2

D PAK (Surface Mount)

LM2576D2T−ADJ

LM2576D2T−ADJG

2

D PAK (Surface Mount)

(Pb−Free)

2

D PAK (Surface Mount)

LM2576D2T−ADJR4

LM2576D2T−ADJR4G

2

D PAK (Surface Mount)

(Pb−Free)

TO−220 (Vertical Mount)

LM2576TV−3.3

TO−220 (Vertical Mount)

(Pb−Free)

LM2576TV−3.3G

TO−220 (Straight Lead)

LM2576T−3.3

TO−220 (Straight Lead)

(Pb−Free)

LM2576T−3.3G

3.3 V

T = −40° to +125°C

J

2

D PAK (Surface Mount)

LM2576D2T−3.3

2

D PAK (Surface Mount)

LM2576D2T−3.3G

(Pb−Free)

2

D PAK (Surface Mount)

LM2576D2TR4−3.3

LM2576D2TR4−3.3G

2

2500 Tape & Reel

D PAK (Surface Mount)

(Pb−Free)

TO−220 (Vertical Mount)

LM2576TV−005

LM2576TV−5G

TO−220 (Vertical Mount)

(Pb−Free)

TO−220 (Straight Lead)

LM2576T−005

50 Units/Rail

TO−220 (Straight Lead)

(Pb−Free)

LM2576T−005G

5.0 V

T = −40° to +125°C

J

2

D PAK (Surface Mount)

LM2576D2T−005

2

D PAK (Surface Mount)

LM2576D2T−005G

(Pb−Free)

2

D PAK (Surface Mount)

LM2576D2TR4−005

LM2576D2TR4−5G

2

2500 Tape & Reel

D PAK (Surface Mount)

(Pb−Free)

TO−220 (Vertical Mount)

LM2576TV−012

TO−220 (Vertical Mount)

(Pb−Free)

LM2576TV−012G

TO−220 (Straight Lead)

LM2576T−012

50 Units/Rail

TO−220 (Straight Lead)

(Pb−Free)

LM2576T−012G

12 V

T = −40° to +125°C

J

2

D PAK (Surface Mount)

LM2576D2T−012

2

D PAK (Surface Mount)

LM2576D2T−012G

(Pb−Free)

2

D PAK (Surface Mount)

LM2576D2TR4−012

LM2576D2TR4−012G

2

2500 Tape & Reel

D PAK (Surface Mount)

(Pb−Free)

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

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24

LM2576

ORDERING INFORMATION

Nominal

Output Voltage

Operating

Temperature Range

†

Device

LM2576TV−015

LM2576TV−015G

Package

Shipping

TO−220 (Vertical Mount)

(Pb−Free)

TO−220 (Straight Lead)

LM2576T−015

LM2576T−15G

15 V

T = −40° to +125°C

J

50 Units/Rail

TO−220 (Straight Lead)

(Pb−Free)

2

D PAK (Surface Mount)

LM2576D2T−015

LM2576D2T−15G

2

D PAK (Surface Mount)

(Pb−Free)

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

MARKING DIAGRAMS

2

TO−220

TV SUFFIX

CASE 314B

TO−220

T SUFFIX

CASE 314D

D PAK

D2T SUFFIX

CASE 936A

LM

2576−xxx

AWLYWWG

2576D2T−xxx

AWLYWWG

LM

2576T−xxx

AWLYWWG

LM

2576T−xxx

AWLYWWG

1

5

1

5

1

5

1

5

xxx = 3.3, 5.0, 12, 15, or ADJ

A

= Assembly Location

WL = Wafer Lot

= Year

WW = Work Week

= Pb−Free Package

Y

G

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25

LM2576

PACKAGE DIMENSIONS

TO−220

TV SUFFIX

CASE 314B−05

ISSUE L

NOTES:

1. DIMENSIONING AND TOLERANCING PER ANSI

Y14.5M, 1982.

2. CONTROLLING DIMENSION: INCH.

3. DIMENSION D DOES NOT INCLUDE

INTERCONNECT BAR (DAMBAR) PROTRUSION.

DIMENSION D INCLUDING PROTRUSION SHALL

NOT EXCEED 0.043 (1.092) MAXIMUM.

C

B

−P−

OPTIONAL

CHAMFER

Q

F

E

A

U

INCHES

DIM MIN MAX

0.613 14.529 15.570

MILLIMETERS

L

S

MIN MAX

V

W

A

B

C

D

E

F

0.572

0.390

0.170

0.025

0.048

0.850

0.067 BSC

0.166 BSC

0.015

0.900

0.320

0.320 BSC

0.140

−−−

0.468

−−−

0.090

0.415

0.180

0.038

0.055

9.906 10.541

K

4.318

0.635

1.219

4.572

0.965

1.397

0.935 21.590 23.749

1.702 BSC

4.216 BSC

G

H

J

0.025

0.381

1.100 22.860 27.940

0.635

5X J

K

L

G

0.365

8.128

8.128 BSC

3.556

9.271

3.886

M

0.24 (0.610)

T

H

N

Q

S

U

V

W

5X D

0.153

0.620

N

−−− 15.748

M

0.10 (0.254)

T

P

0.505 11.888 12.827

0.735

0.110

SEATING

PLANE

−−− 18.669

2.286 2.794

−T−

TO−220

T SUFFIX

CASE 314D−04

ISSUE F

NOTES:

SEATING

−T−

PLANE

1. DIMENSIONING AND TOLERANCING PER ANSI

Y14.5M, 1982.

B

C

2. CONTROLLING DIMENSION: INCH.

3. DIMENSION D DOES NOT INCLUDE

INTERCONNECT BAR (DAMBAR) PROTRUSION.

DIMENSION D INCLUDING PROTRUSION SHALL

NOT EXCEED 10.92 (0.043) MAXIMUM.

−Q−

DETAIL A−A

B1

E

A

U

K

INCHES

DIM MIN MAX

MILLIMETERS

MIN MAX

L

A

0.572

0.390

0.613 14.529 15.570

0.415 9.906 10.541

0.415 9.525 10.541

1 2 3 4 5

B

B1 0.375

C

D

E

G

H

J

0.170

0.025

0.048

0.180 4.318

0.038 0.635

0.055 1.219

1.702 BSC

0.112 2.210

0.025 0.381

4.572

0.965

1.397

0.067 BSC

0.087

0.015

0.977

0.320

0.140

0.105

2.845

0.635

J

H

G

K

L

1.045 24.810 26.543

D 5 PL

0.365 8.128

0.153 3.556

0.117 2.667

9.271

3.886

2.972

Q

U

M

0.356 (0.014)

T

Q

B

B1

DETAIL A−A

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26

LM2576

PACKAGE DIMENSIONS

D²PAK

D2T SUFFIX

CASE 936A−02

ISSUE C

NOTES:

−T−

TERMINAL 6

1. DIMENSIONING AND TOLERANCING PER ANSI

Y14.5M, 1982.

2. CONTROLLING DIMENSION: INCH.

3. TAB CONTOUR OPTIONAL WITHIN DIMENSIONS A

AND K.

4. DIMENSIONS U AND V ESTABLISH A MINIMUM

MOUNTING SURFACE FOR TERMINAL 6.

5. DIMENSIONS A AND B DO NOT INCLUDE MOLD

FLASH OR GATE PROTRUSIONS. MOLD FLASH

AND GATE PROTRUSIONS NOT TO EXCEED 0.025

(0.635) MAXIMUM.

OPTIONAL

CHAMFER

A

E

U

S

K

V

B

H

1

2

3

4 5

M

L

INCHES

MILLIMETERS

DIM

A

B

C

D

E

MIN

MAX

0.403

0.368

0.180

0.036

0.055

MIN

9.804

9.042

4.318

0.660

1.143

MAX

10.236

9.347

4.572

0.914

1.397

D

P

N

0.386

0.356

0.170

0.026

0.045

M

0.010 (0.254)

T

G

R

G

H

K

L

M

N

P

0.067 BSC

1.702 BSC

14.707

1.270 REF

0.539

0.579 13.691

0.050 REF

0.000

0.088

0.018

0.058

0.010

0.102

0.026

0.078

0.000

2.235

0.457

1.473

0.254

2.591

0.660

1.981

C

R

S

U

V

5_ REF

0.116 REF

0.200 MIN

0.250 MIN

2.946 REF

5.080 MIN

6.350 MIN

SOLDERING FOOTPRINT*

8.38

0.33

1.702

0.067

10.66

0.42

1.016

0.04

3.05

0.12

16.02

0.63

mm

inches

ǒ

Ǔ

SCALE 3:1

*For additional information on our Pb−Free strategy and soldering

details, please download the ON Semiconductor Soldering and

Mounting Techniques Reference Manual, SOLDERRM/D.

http://onsemi.com

27

LM2576

ON Semiconductor and

are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice

to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability

arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.

“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All

operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights

nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications

intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should

Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,

and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death

associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal

Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.

PUBLICATION ORDERING INFORMATION

LITERATURE FULFILLMENT:

N. American Technical Support: 800−282−9855 Toll Free

USA/Canada

ON Semiconductor Website: http://onsemi.com

Order Literature: http://www.onsemi.com/litorder

Literature Distribution Center for ON Semiconductor

P.O. Box 61312, Phoenix, Arizona 85082−1312 USA

Phone: 480−829−7710 or 800−344−3860 Toll Free USA/Canada

Fax: 480−829−7709 or 800−344−3867 Toll Free USA/Canada

Email: orderlit@onsemi.com

Japan: ON Semiconductor, Japan Customer Focus Center

2−9−1 Kamimeguro, Meguro−ku, Tokyo, Japan 153−0051

Phone: 81−3−5773−3850

For additional information, please contact your

local Sales Representative.

LM2576/D

http://onsemi.com

28


型号：	LM2576D2TR4-012G
厂家：	ONSEMI
描述：	3.0 A, 15 V, Step−Down Switching Regulator 3.0 A， 15 V ，降压型开关稳压器稳压器开关式稳压器或控制器电源电路开关式控制器 PC
文件：	总28页 (文件大小：276K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LM2576D2TR4-012G [ONSEMI]

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