LM2576-5.0BU_技术文档

LM2576

Micrel

LM2576

52kHz Simple 3A Buck Voltage Regulator

General Description

Features

The LM2576 series of monolithic integrated circuits provide

all the active functions for a step-down (buck) switching

regulator.Fixedversionsareavailablewitha3.3V,5V,or12V

fixed output. Adjustable versions have an output voltage

rangefrom1.23Vto37V. Bothversionsarecapableofdriving

a 3A load with excellent line and load regulation.

• 3.3V, 5V, 12V, and adjustable output versions

• Voltage over specified line and load conditions:

Fixed version: ±3% max. output voltage

Adjustable version: ±2% max. feedback voltage

• Guaranteed 3A output current

• Wide input voltage range:

4V to 40V

• Wide output voltage range

1.23V to 37V

These regulators are simple to use because they require a

minimumnumberofexternalcomponentsandincludeinternal

frequency compensation and a fixed-frequency oscillator.

The LM2576 series offers a high efficiency replacement for

popular three-terminal adjustable linear regulators. It

substantially reduces the size of the heat sink, and in many

cases no heat sink is required.

• Requires only 4 external components

• 52kHz fixed frequency internal oscillator

• Low power standby mode I typically < 200µA

Q

• 80% efficiency (adjustable version typically > 80%)

• Uses readily available standard inductors

• Thermal shutdown and current limit protection

• 100% electrical thermal limit burn-in

Astandardseriesofinductorsavailablefromseveraldifferent

manufacturers are ideal for use with the LM2576 series. This

feature greatly simplifies the design of switch-mode power

supplies.

The feedback voltage is guaranteed to ±2% tolerance for

adjustable versions, and the output voltage is guaranteed to

±3% for fixed versions, within specified input voltages and

outputloadconditions.Theoscillatorfrequencyisguaranteed

to ±10%. External shutdown is included, featuring less than

200µA standby current. The output switch includes cycle-by-

cycle current limiting and thermal shutdown for full protection

under fault conditions.

Applications

• Simple high-efficiency step-down (buck) regulator

• Efficient pre-regulator for linear regulators

• On-card switching regulators

• Positive to negative converter (inverting Buck-Boost)

• Isolated Flyback Converter using minimum number of

external components

• Negative Boost Converter

Typical Applications

870 20

7V–40V

Unregulated

DC Input

7V–40V

Unregulated

DC Input

+5V, 3A

Regulated

Output

+5V, 3A

Regulated

Output

4

Feedback

L1

Feedback

L1

1

LM2576-5.0

LM2576

3 5

Output

2

Output

2

+V_IN

100µH

+

R2 3.09k

R1 1k

3

5

C_IN

100µF

Gnd On/Off

D1

1N5822

D1

1N5822

C_OUT

1000µF

C_OUT

1000µF

100µF

Note: Pin numbers are for TO-220 Package

R2

V

_OUT= 1.23 1 +

( )

R1

Fixed Regulator in Typical Application

Adjustable Regulator in Fixed Output Application

4-120

October 1998

LM2576

Micrel

Ordering Information

Part Number^‡

LM2576BT*^†

Temperature Range

–40°C to +85°C

Package

5-lead TO-220

5-lead TO-263

LM2576-3.3BT^†

LM2576-5.0BT^†

LM2576-12BT^†

LM2576BU*

LM2576-3.3BU

LM2576-5.0BU

LM2576-12BU

* Adjustable output regulators.

†

Contact factory for bent or staggered leads option.

4

Pin Configurations

5-LEAD TO-220 (T)

5-LEAD TO-263 (U)

GND

5- ON/OFF

4- FEEDBACK

3- GROUND

2- OUTPUT

4- FEEDBACK

3- GROUND

2- OUTPUT

1- V

IN

October 1998

4-121

LM2576

Micrel

Absolute Maximum Ratings (Note 1)

Operating Ratings

Maximum Supply Voltage

45V

Temperature Range

Supply Voltage

–40°C ≤ T_J≤ +125°C

ON/OFF Pin Input Voltage

Output Voltage to Ground (Steady State)

Power Dissipation

Storage Temperature Range

Minimum ESD Rating

–0.3V ≤ V ≤ +40V

–1V

Internally Limited

–65°C to +150°C

40V

C = 100pF, R = 1.5kΩ

FB Pin

2 kV

1 kV

Lead Temperature (soldering, 10 sec.)

Maximum Junction Temperature

260°C

150°C

Electrical Characteristics Specifications with standard typeface are for T_J= 25°C, and those with boldface type apply

over full Operating Temperature Range. Unless otherwise specified, V_IN= 12V, and I_LOAD= 500mA.

LM2576

Symbol

Parameter

Conditions

Typ

Limit

Units

(Note 2)

(Limits)

SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1

V_OUT

η

Feedback Voltage

V_IN= 12V , I_LOAD= 0.5A

_OUT= 5V

1.230

V

1.217

1.243

V(min)

V(max)

Feedback Voltage

LM2576

0.5A ≤ I_LOAD≤ 3A, 6V ≤ V_IN≤ 40V

V_OUT= 5V

V

1.193/1.180

1.267/1.280

V(min)

V(max)

Efficiency

V_IN= 12V, I_LOAD= 3A, V_OUT= 5V

82

%

SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1

V_OUT

η

Output Voltage

V_IN= 12V , I_LOAD= 0.5A

_OUT= 3.3V

3.3

V

3.234

3.366

V(min)

V(max)

Output Voltage

LM2576-3.3

0.5A ≤ I_LOAD≤ 3A, 6V ≤ V_IN≤ 40V

V_OUT= 3.3V

3.3

V

3.168/3.135

3.432/3.465

V(min)

V(max)

Efficiency

V_IN= 12V, I_LOAD= 3A

75

%

SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1

V_OUT

η

Output Voltage

V_IN= 12V , I_LOAD= 0.5A

V_OUT= 5V

5.0

V

4.900

5.100

V(min)

V(max)

Output Voltage

LM2576-5.0

0.5A ≤ I_LOAD≤ 3A, 8V ≤ V_IN≤ 40V

V_OUT= 5V

5.0

V

4.800/4.750

5.200/5.250

V(min)

V(max)

Efficiency

V_IN= 12V, I_LOAD= 3A

82

12

%

SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1

V_OUT

η

Output Voltage

V_IN= 25V , I_LOAD= 0.5A

V_OUT= 12V

V

11.760

12.240

V(min)

V(max)

Output Voltage

LMLM2576-12

0.5A ≤ I_LOAD≤ 3A, 15V ≤ V_IN≤ 40V

V_OUT= 12V

12

88

V

11.520/11.400

12.480/12.600

V(min)

V(max)

Efficiency

V_IN= 25V, I_LOAD= 3A

%

4-122

October 1998

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Electrical Characteristics (continued)

LM2576

Units

Symbol

Parameter

Conditions

Typ

Limit

(Limits)

(Note 2)

DEVICE PARAMETERS, ADJUSTABLE REGULATOR

I_BFeedback Bias Current V_OUT= 5V

DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS

50

52

100/500

nA

f_O

Oscillator Frequency

kHz

47/42

58/63

kHz (min)

kHz (max)

V_SAT

DC

Saturation Voltage

Max Duty Cycle (ON)

Current Limit

I_OUT= 3A (Note 4)

(Note 5)

1.4

98

V

1.8/2.0

V(max)

%

%(min)

93

I_CL

Peak Current, t_ON≤ 3µs (Note 4)

5.8

A

4.2/3.5

6.9/7.5

A(min)

A(max)

I_L

Output Leakage Current V_IN= 40V, (Note 6),

(Note 6)

Output = 0V

Output = –1V

2

mA(max)

mA

mA(max)

7.5

5

30

I_Q

Quiescent Current

(Note 6)

mA

10

mA(max)

4

I_STBY

Standby Quiescent

Current

ON/OFF Pin = 5V (OFF)

50

µA

200

µA(max)

θ_JA

θ_JC

Thermal Resistance

T,U Package, Junction to Ambient (Note 7) 65

T,U Package, Junction to Ambient (Note 8) 45

°C/W

T,U Package, Junction to Case

2

October 1998

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Electrical Characteristics (continued)

LM2576

Units

Symbol

Parameter

Conditions

Typ

Limit

(Limits)

(Note 2)

ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1

V_IH

V_IL

ON/OFF Pin Logic

Input Level

V_OUT= 0V

V_OUT= 5V

1.4

1.2

2.2/2.4

1.0/0.8

V(min)

V(max)

I_IH

ON /OFF Pin Logic

Current

ON /OFF Pin = 5V (OFF)

4

µA

µA(max)

30

10

I_IL

ON/OFF Pin = 0V (ON)

0.01

µA

µA(max)

Note 1: AbsoluteMaximumRatingindicatelimitsbeyondwhichdamagetothedevicemayoccur. OperatingRatingsindicateconditionsforwhichthedevice

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% production tested. All limits at temperature extreme are guaranteed via testing.

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

LM2576/LM1576 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of Electrical

Characteristics.

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

Note 5: Feedback (pin 4) removed from output and connected to 0V.

Note 6: Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF.

Note 7: Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/2" leads in a socket, or

on PC board with minimum copper area.

Note 8: Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/4" leads soldered to PC

board containing approximately 4 square inches of copper area surrounding the leads.

Note 9: Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower

thermal resistance further.

Typical Performance Characteristics

Normalized

Feedback Voltage

vs Duty Cycle*

Feedback Voltage*

20

15

10

5

25

20

15

ILOAD = 200 mA

V

= 12V

IN

I

= 200mA

LOAD

Normalized to T = 25˚C

J

10

5

VIN = 40V

0

-5

VIN = 7V

-10

-15

-20

-25

-75 -50 -25

0

25 50 75 100125150

0

20

40

60

80

100

JUNCTION TEMPERATURE (˚C)

DUTY CYCLE (%)

* Adjustable version only

4-124

October 1998

LM2576

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Typical Performance Characteristics (continued) (Circuit of Figure 1)

Supply Current

vs. Duty Cycle

Standby

Quiescent Current

Supply Current

20

18

20.0

17.5

200

150

Measured at

Ground Pin

V

= 40V

IN

T

= 25˚C

J

16

14

12

10

8

15.0

12.5

10.0

7.5

5.0

2.5

0

V

= 5V

OUT

V

= 5V

ON/OFF

100

50

0

I

= 200 mA

LOAD

V

= 12V

IN

I

to 1A

LOAD

V

from 7V to 40V

6

IN

4

0

10 20

30

40 50

60

0

20

40

60

80

100

-75 -50 -25 0 25 50 75 100 125150

INPUT VOLTAGE (V)

DUTY CYCLE (%)

JUNCTION TEMPERATURE (˚C)

Switch

Saturation Voltage

Current Limit

Efficiency

6.5

1.5

1.4

1.2

1.0

100

95

V

= 12V

IN

V

= 12V

1A

3A

6.0

5.5

OUT

90

-55˚C

85

80

200 mA

0.8

0.6

200 mA

25˚C

5.0

4.5

75

150˚C

0.4

0.2

0

70 1A

4

V

= 3V

OUT

65 3A

60

4.0

-75 -50 -25

0

25 50 75 100125150

0

0.5 1.0 1.5 2.0 2.5 3.0

SWITCH CURRENT (A)

0

5

10 15 20 25 30 35 40

INPUT VOLTAGE (V)

JUNCTION TEMPERATURE (˚C)

Minimum Operating

Voltage

Line Regulation

Feedback Pin Current

5.0

4.5

14

12

100

75

Normalized to V = 10V

IN

V

= 5V

OUT

4.0

3.5

3.0

2.5

2.0

1.5

1.0

10

8

I

= 500mA

50

25

LOAD

= 25

T

J

6

4

0

2

-25

-50

-75

-100

0

V

= 1.23V

OUT

= 200 mA

-2

-4

I

LOAD

0.5

0

-6

-75 -50 -25

0

25 50 75 100125150

0

5

10 15

20

25

30

-75 -50 -25

0

25 50 75 100 125150

JUNCTION TEMPERATURE (˚C)

INPUT VOLTAGE (V)

JUNCTION TEMPERATURE (˚C)

Normalized

Oscillator Frequency

Dropout Voltage

Output Voltage

2.0

1.5

1.0

100

75

+8

+6

V

IN

= 12V

Normalized at 25˚C

I

= 3A

L1 = 330 µH

LOAD

I

= 200mA

LOAD

Normalized to T = 25˚C

J

+4

+2

0

50

I

= 1A

25

0

LOAD

-25

-50

-2

V

= 40V

IN

I = 200 mA

LOAD

-4

0.5

0

-75

--6

-8

V

= 12V

IN

0 25 50 75 100125150

-100

-75 -50 -25

0

25 50 75 100125150

-75 -50 -25

0

25 50 75 100125150

-75 -50 -25

JUNCTION TEMPERATURE (˚C)

October 1998

4-125

LM2576

Micrel

Typical Performance Characteristics (Circuit of Figure 1)

Load Transient Response

+100mV

0

Output

Voltage

Change

-100mV

3A

2A

1A

0

Output

Current

100 µS/div.

Switching Waveforms

50V

0

A

B

4A

2A

0

4A

2A

0

C

D

5 µS/div.

= 45V

V

= 5V V

IN

OUT

A: Output pin voltage 50V/div

B: Output pin current 2A/div

C: Inductor current 2A/div

D: Output ripple voltage 50 mV/div., AC coupled

Horizontal Time Base: 5µS/div

4-126

October 1998

LM2576

Micrel

Test Circuits and Layout Guidelines

FEEDBACK

+V

4

2

IN

V

5.00V

OUT

LM2575

L1

C

— 100µF, 75V Aluminum Electrolytic

IN

OUTPUT

1

— 470µF, 15V Aluminum Electrolytic

OUT

D1 — Schottky, MBR360

7V - 40V

UNREGULATED

DC INPUT

330 µH

+

100 µF

L1 — 330µH, 415-0926 (AIE)

R1 — 1k, 0.01%

+

R2

R1

L

C

470µF

GND

3

ON/OFF 5

OUT

O

A

D

D1

MBR360

R2 — 3.065k, 0.01%

5-pin TO-220 socket—2936 (Loranger Mfg. Co.)

4-pin TO-3 socket—8112-AG7 (Augat Inc.)

C

IN

FEEDBACK

OUTPUT

+V

4

2

IN

V

5.00V

OUT

LM2575-5.0

L1

C

— 100µF, 75V Aluminum Electrolytic

IN

1

— 330µF, 15V Aluminum Electrolytic

OUT

D1 — Schottky, 11DQ06

7V - 40V

UNREGULATED

DC INPUT

330 µH

+

L1 — 100µH, 415-0926 (AIE)

100 µF

+

L

C

220µF

GND

3

ON/OFF 5

OUT

5-pin TO-220 socket—2936 (Loranger Mfg. Co.)

4-pin TO-3 socket—8112-AG7 (Augat Inc.)

O

A

D

D1

11DQ06

C

IN

Note: Pin numbers are for TO-220 Package

Figure 1.

4

As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generatevoltage transients

which can cause problems. For minimal stray inductance and ground loops, the length of the leads indicated by heavy lines should be kept as

short as possible. Single-point grounding (as indicated) or ground plane construction should be used for best results.

Block Diagrams

INTERNAL

V

IN

ON/OFF

5

ON/OFF

5

ON/OFF

1

4

1

4

REGULATOR

FEED-

BACK

FIXED GAIN

ERROR AMP

FIXED GAIN

ERROR AMP

3.1k

1.0k

FEED-

BACK

3 AMP

SWITCH

3 AMP

SWITCH

COMPARATOR

+

-

+

-

+

-

+

-

DRIVER

2

3

2

3

OUTPUT

GND

OUTPUT

GND

1.23V

BAND-GAP

REFERENCE

1.23V

BAND-GAP

REFERENCE

52 kHz

OSCILLATOR

THERMAL

SHUTDOWN

CURRENT

LIMIT

52 kHz

OSCILLATOR

THERMAL

SHUTDOWN

CURRENT

LIMIT

RESET

Note: Pin numbers are for the TO-220 package

Fixed Regulator

Adjustable Regulator

October 1998

4-127


型号：	LM2576-5.0BU
厂家：	MICREL SEMICONDUCTOR
描述：	52kHz Simple 3A Buck Voltage Regulator 52kHz简单的3A降压稳压器稳压器
文件：	总8页 (文件大小：92K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LM2576-5.0BU [MICREL]

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