Datasheet LM2575BWM, LM2575BU, LM2575BT, LM2575BN, LM2575-5.0BU Datasheet (MICREL)

LM2575 Micrel

LM2575

52kHz Simple 1A Buck Regulator

General Description

The LM2575 series of monolithic integrated circuits provide
all the active functions for a step-down (buck) switching
regulator. Fixed versions are available with a 3.3V, 5V, 12V,
fixed output. Adjustable versions have an output voltage
range from 1.23V to 37V. Both versions are capable of driving
a 1A load with excellent line and load regulation.

These regulators are simple to use because they require a
minimum number of external components and include internal
frequency compensation and a fixed-frequency oscillator.

The LM2575 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.

A standard series of inductors available from several different
manufacturers are ideal for use with the LM2575 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
output load conditions. The oscillator frequency is guaranteed
to ±10%. External shutdown is included, featuring less than
200µA standby current. The output switch includes cycle-by­cycle current limiting and thermal shutdown for full protection
under fault conditions.

Features

• 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 1A output current

• Wide input voltage range:
4V to 40V

• Wide output voltage range

1.23V to 37V

• Requires only 4 external components

• 52kHz fixed frequency internal oscillator

• Low power standby mode IQ typically < 200µA

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

• Uses readily available standard inductors

• Thermal shutdown and current limit protection

• 100% electrical thermal limit burn-in

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

7V–40V

Unregulated

DC Input

C

IN

100µF

Note: Pin numbers are for TO-220 Package

+V

+

1

LM2575-5.0

IN

3

Gnd5On/Off

4

Output
2

Feedback

L1

330µH

D1
1N5822

+5V, 1A

Regulated

Output

+

C

OUT

330µF

7V–40V

Unregulated

DC Input

C

IN

100µF

Note: Pin numbers are for TO-220 Package

V

OUT

1

+V

IN

+

= 1.23 1 +

3

Gnd5On/Off

( )

LM2575

R2
R1

4

Output
2

Feedback

L1

330µH

D1
1N5822

+

C

OUT

330µF

Regulated

Fixed Regulator in Typical Application Adjustable Regulator in Fixed Output Application

August 1999 1 M2575

870 20

+5V, 1A

Output

R2 3.09k
R1 1k

LM2575 Micrel

Ordering Information

Part Number

LM2575BN* –40°C to +85 °C 16-pin Plastic DIP
LM2575-3.3BN –40°C to +85 °C 16-pin Plastic DIP
LM2575-5.0BN –40°C to +85 °C 16-pin Plastic DIP
LM2575-12BN –40°C to +85 °C 16-pin Plastic DIP
LM2575BWM* –40°C to +85°C 24-pin Wide SOIC
LM2575-3.3BWM –40°C to +85°C 24-pin Wide SOIC
LM2575-5.0BWM –40°C to +85°C 24-pin Wide SOIC
LM2575-12BWM –40°C to +85°C 24-pin Wide SOIC
LM2575BT*
LM2575-3.3BT
LM2575-5.0BT
LM2575-12BT
LM2575BU* –40°C to +85°C 5-lead TO-263
LM2575-3.3BU –40°C to +85°C 5-lead TO-263
LM2575-5.0BU –40°C to +85°C 5-lead TO-263
LM2575-12BU –40°C to +85°C 5-lead TO-263

* Adjustable output regulators.

†

Contact factory for bent or staggered leads option.

‡

Temperature Range Package

†

†

†

†

–40°C to +85°C 5-lead TO-220
–40°C to +85°C 5-lead TO-220
–40°C to +85°C 5-lead TO-220
–40°C to +85°C 5-lead TO-220

Pin Configurations

OUTPUT

GND

5-LEAD TO-220 (T)

GND

16-LEAD DIP (N)

1

NC

2

NC

3
4

NC

5
6

NC

7

FB

8

NC

5- ON/OFF
4- FEEDBACK
3- GROUND
2- OUTPUT
1- V

IN

16

V

IN

15

NC

14

GND

13

GND

12

GND

11

GND

10

NC

9

ON/OFF

5-LEAD TO-263 (U)

GND

24-LEAD SOIC (WM)

NC
NC
NC
NC
NC

FB

NC

NC

1
2
3
4
5
6
7
8

9
10
11
12

PWR GND

SIG GND

ON/OFF

PWR GND

5- ON/OFF
4- FEEDBACK
3- GROUND
2- OUTPUT
1- V

IN

24
23
22
21
20
19
18
17

16
15
14
13

NC
NC
NC
NC
NC
NC
OUTPUT
OUTPUT
NC
V

IN

V

IN

NC

LM2575 2 August 1999

LM2575 Micrel

Absolute Maximum Ratings (Note 1)

Maximum Supply Voltage 45V
ON/OFF Pin Input Voltage –0.3V ≤ V ≤ +40V

Operating Ratings

Temperature Range –40°C ≤ TJ ≤ +125°C

Supply Voltage 40V
Output Voltage to Ground (Steady State) –1V
Power Dissipation Internally Limited
Storage Temperature Range –65°C to +150°C
Minimum ESD Rating

C = 100pF, R = 1.5kΩ 2 kV

FB Pin 1 kV
Lead Temperature (soldering, 10 sec.) 260°C
Maximum Junction Temperature 150°C

Electrical Characteristics Specifications with standard typeface are for T

over full Operating Temperature Range. Unless otherwise specified, V

= 12V, and I

IN

= 25°C, and those with boldface type apply

J

= 200mA.

LOAD

LM2575

Symbol Parameter Conditions Typ Limit Units

(Note 2) (Limits)

SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit

V

OUT

V

OUT

η Efficiency VIN = 12V, I
SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit
V

OUT

V

OUT

η Efficiency VIN = 12V, I
SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit
V

OUT

V

OUT

η Efficiency VIN = 12V, I
SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit
V

OUT

V

OUT

η Efficiency VIN = 25V, I

Feedback Voltage VIN = 12V , I

V

= 5V 1.217 V(min)

OUT

Feedback Voltage 0.2A ≤ I
LM2575 V

LOAD

= 5V 1.193/1.180 V(min)

OUT

Output Voltage VIN = 12V , I

V

= 3.3V 3.234 V(min)

OUT

Output Voltage 0.2A ≤ I
LM2575-3.3 V

LOAD

= 3.3V 3.168/3.135 V(min)

OUT

Output Voltage VIN = 12V , I

V

= 5V 4.900 V(min)

OUT

Output Voltage 0.2A ≤ I
LM2575-5.0 V

LOAD

= 5V 4.800/4.750 V(min)

OUT

Output Voltage VIN = 25V , I

V

= 12V 11.760 V(min)

OUT

Output Voltage 0.2A ≤ I
LM2575-12 V

LOAD

= 12V 11.520/11.400 V(min)

OUT

= 0.2A 1.230 V

LOAD

≤ 1A, 8V ≤ VIN ≤ 40V 1.230 V

LOAD

= 1A, V

= 5V 82 %

OUT

Figure 1

= 0.2A 3.3 V

LOAD

≤ 1A, 8V ≤ VIN ≤ 40V 3.3 V

= 1A 75 %

LOAD

Figure 1

= 0.2A 5.0 V

LOAD

≤ 1A, 8V ≤ VIN ≤ 40V 5.0 V

= 1A 82 %

LOAD

Figure 1

= 0.2A 12 V

LOAD

≤ 1A, 15V ≤ VIN ≤ 40V 12 V

= 1A 88 %

LOAD

Figure 1

1.243 V(max)

1.267/1.280 V(max)

3.366 V(max)

3.432/3.465 V(max)

5.100 V(max)

5.200/5.250 V(max)

12.240 V(max)

12.480/12.600 V(max)

August 1999 3 M2575

LM2575 Micrel

Electrical Characteristics (continued)

LM2575 Units

Symbol Parameter Conditions Typ Limit (Limits)

(Note 2)

DEVICE PARAMETERS, ADJUSTABLE REGULATOR

I

B

DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS

f

O

V

SAT

DC Max Duty Cycle (ON) (Note 5) 98 %

I

CL

I

L

I

Q

I

STBY

θ

JA

θ

JA

θ

JC

θ

JA

θ

JA

Feedback Bias Current V

= 5V 50 100/500 nA

OUT

Oscillator Frequency 52 kHz

47/42 kHz (min)
58/63 kHz (max)

Saturation Voltage I

= 1A (Note 4) 0.9 V

OUT

1.2/1.4 V(max)

93 %(min)

Current Limit Peak Current, t

≤ 3µs (Note 4) 2.2 A

ON

1.7/1.3 A(min)

3.0/3.2 A(max)

Output Leakage Current VIN = 40V, (Note 6), Output = 0V 2 mA(max)

Output = –1V 7.5 mA

(Note 6) Output = –1V 30 mA(max)

Quiescent Current (Note 6) 5 mA

10 mA(max)

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

Thermal Resistance T Package, Junction to Ambient (Note 7) 65 °C/W

T Package, Junction to Ambient (Note 8) 45
T Package, Junction to Case 2
N Package, Junction to Ambient (Note 9) 85
WM Package, Junction to Amb. (Note 9) 100

LM2575 4 August 1999

LM2575 Micrel

LM2575 Units

Symbol Parameter Conditions Typ Limit (Limits)

(Note 2)

ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit

V

IH

V

IL

I

IH

I

IL

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

Note 2: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face) . All room temperature limits are

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

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

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

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

ON/OFF Pin Logic V
Input Level V

= 0V 1.4 2.2/2.4 V(min)

OUT

= 5V 1.2 1.0/0.8 V(max)

OUT

ON /OFF Pin Logic ON /OFF Pin = 5V (OFF) 4 µA
Current 30 µA(max)

ON/OFF Pin = 0V (ON) 0.01 µA

is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical
Characteristics.

100% production tested. All limits at temperature extreme are guaranteed via testing.

LM2575/LM1575 is used as shown in
Characteristics.

on PC board with minimum copper area.

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

thermal resistance further.

Figure 1

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

Figure 1

10 µA(max)

Typical Performance Characteristics

Normalized
Feedback Voltage*

25
20
15
10

5
0

-5

-10

-15

-20

NORMALIZED FEEDBACK VOLTAGE (mV)

-25

-75 -50 -25 0 25 50 75 100125150

JUNCTION TEMPERATURE (˚C)

* Adjustable version only

VIN = 12V

I

= 200mA

LOAD

Normalized to TJ = 25˚C

Feedback Voltage
vs Duty Cycle*

20
15
10

5
0

-5

-10

-15

FEEDBACK VOLTAGE CHANGE (mV)

-20
0 20 40 60 80 100

I

LOAD

VIN = 7V

DUTY CYCLE (%)

= 200 mA

VIN = 40V

August 1999 5 M2575

LM2575 Micrel

Typical Performance Characteristics (continued) (Circuit of

Supply Current

20
18

16
14
12
10

8

SUPPLY CURRENT (mA)

6
4

0102030405060

Measured at

Ground Pin

TJ = 25˚C

V

I

to 1A

LOAD

INPUT VOLTAGE (V)

Current Limit

3

2

1

OUTPUT CURRENT (A)

0

-75

-50 -25 0 25 50 75 100125 150

JUNCTION TEMPERATURE (˚C)

= 5V

OUT

VIN = 25V

Supply Current
vs. Duty Cycle

20.0

17.5

15.0

12.5

10.0
I

7.5

5.0

SUPPLY CURRENT (mA)

2.5
0

0 2040 6080100

= 200 mA

LOAD

VIN from 7V to 40V

DUTY CYCLE (%)

Switch
Saturation Voltage

1.2

1.0

-55˚C

-40˚C

0.8
25˚C

0.6

125˚C

SATURATION VOLTAGE (V)

150˚C

0.4
0

0.2 0.4 0.6 0.8 1.0

SWITCH CURRENT (A)

Figure 1

)

Standby
Quiescent Current

200

150

100

50

STANDBY QUIESCENT CURRENT (µA)

0

-75

-50 -25 0 25 50 75 100 125150

Efficiency

100

95
90
85

200 mA

80
75

EFFICIENCY (%)

70
65
60

0 5 10 15 20 25 30 35 40

VIN = 40V

V

= 5V

ON/OFF

VIN = 12V

JUNCTION TEMPERATURE (˚C)

V

= 12V

OUT

200 mA

1A

V

= 3V

OUT

INPUT VOLTAGE (V)

1A

Minimum Operating
Voltage

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

INPUT VOLTAGE (V)

1.0

0.5
0

-75 -50 -25 0 25 50 75 100125150

JUNCTION TEMPERATURE (˚C)

V

I

LOAD

OUT

Normalized
Output Voltage

100

75
50
25

0

-25

-50

-75

OUTPUT VOLTAGE CHANGE (mV)

-100

-75 -50 -25 0 25 50 75 100125150

JUNCTION TEMPERATURE (˚C)

VIN = 12V

I

= 200mA

LOAD

Normalized to TJ = 25˚C

= 1.23V

= 200 mA

Line Regulation

14

Normalized to VIN = 10V

12

V

= 5V

OUT

10

I

= 500mA

LOAD

8

TJ = 25

6
4
2
0

-2

-4

NORMALIZED FEEDBACK VOLTAGE (mV)

-6
0

51015202530

INPUT VOLTAGE (V)

Oscillator Frequency

+8
+6

+4
+2

0

-2

-4

--6

NORMALIZED FREQUENCY (%)

-8

-75

-50 -25 0 25 50 75 100 125150

JUNCTION TEMPERATURE (˚C)

Normalized at 25˚C

VIN = 40V

VIN = 12V

Feedback Pin Current

100

75
50
25

0

-25

-50

-75

STANDBY QUIESCENT CURRENT (µA)

-100

-75

-50 -25 0 25 50 75 100 125150

JUNCTION TEMPERATURE (˚C)

Dropout Voltage

2.0

I

= 1A

LOAD

1.5

1.0

I

= 200 mA

LOAD

0.5

INPUT-OUTPUT DIFFERENTIAL (V)

0

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

JUNCTION TEMPERATURE (˚C)

∆V

= 5%

OUT

R

= 0.2Ω

IND

LM2575 6 August 1999

LM2575 Micrel

Typical Performance Characteristics (Circuit of

Load Transient Response

+100mV

Output

Voltage
Change

Output

Current

V

OUT

= 5V

–100mV

1.0A

0.5A

0

0

100µS/div.

Test Circuits and Layout Guidelines

FEEDBACK

7V - 40V

UNREGULATED

DC INPUT

+

100 µF

C

IN

+V

IN

1

LM2575

3GND 5ON/OFF

4

OUTPUT

2

L1

330 µH

D1
MBR360

Figure 1

+

C

OUT

470µF

)

Switching Waveforms

A

10V

0

B

1A

0

1A

C

.5A

0

D

V

OUT

A: Output pin voltage 10V/div
B: Output pin current 1A/div

C: Inductor current 0.5A/div
D: Output ripple voltage 20 mV/div. AC coupled

Horizontal Time Base: 5µs/div

R2

R1

= 5V

V

5.00V

OUT

V

= 20V

IN

CIN — 100µF, 75V Aluminum Electrolytic

— 470µF, 15V Aluminum Electrolytic

C

OUT

D1 — Schottky, MBR360

L
O
A
D

L1 — 330µH, 415-0926 (AIE)
R1 — 1k, 0.01%
R2 — 3.065k, 0.01%
5-pin TO-220 socket—2936 (Loranger Mfg. Co.)
4-pin TO-3 socket—8112-AG7 (Augat Inc.)

FEEDBACK

+V

IN

LM2575-5.0

1

7V - 40V

UNREGULATED

DC INPUT

+

100 µF

C

IN

Note: Pin numbers are for TO-220 Package

3GND 5ON/OFF

4

OUTPUT

2

L1

330 µH

D1
MBR360

+

C

OUT

220µF

Figure 1.

V

OUT

5.00V

CIN — 100µF, 75V Aluminum Electrolytic
C

— 330µF, 15V Aluminum Electrolytic

OUT

D1 — Schottky, MBR360

L
O
A
D

L1 — 330µH, 415-0926 (AIE)
5-pin TO-220 socket—2936 (Loranger Mfg. Co.)
4-pin TO-3 socket—8112-AG7 (Augat Inc.)

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

V

FEED­BACK

IN

1

4

BAND-GAP

REFERENCE

3.1k

1.0k

1.23V

FIXED GAIN
ERROR AMP

+

-

52 kHz

OSCILLATOR

INTERNAL

REGULATOR

COMPARATOR

+

-

RESET

THERMAL

SHUTDOWN

ON/OFF

DRIVER

CURRENT

LIMIT

1 AMP
SWITCH

5

2

3

ON/OFF

OUTPUT

GND

V

FEED­BACK

IN

1

FIXED GAIN
ERROR AMP

4

+

-

1.23V

BAND-GAP

REFERENCE

52 kHz

OSCILLATOR

INTERNAL

REGULATOR

COMPARATOR

+

-

RESET

THERMAL

SHUTDOWN

ON/OFF

DRIVER

CURRENT

LIMIT

1 AMP
SWITCH

ON/OFF

5

2

OUTPUT

3

GND

Note: Pin numbers are for the TO-220 package

Fixed Regulator Adjustable Regulator

August 1999 7 M2575