April 2005

7

M9999-042205

LM2575

Micrel, Inc.

LM2575

+

100 µF

1

3

GND

5

ON/OFF

2

OUTPUT

4

FEEDBACK

L1

330 µH

+

D1

MBR360

470µF

R2

R1

5.00V

7V - 40V

UNREGULATED

DC INPUT

L

O

A

D

D1 — Schottky, MBR360

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.)

LM2575-5.0

+

100 µF

1

3

GND

5

ON/OFF

2

OUTPUT

4

FEEDBACK

L1

330 µH

+

D1

MBR360

220µF

5.00V

Note: Pin numbers are for TO-220 Package

7V - 40V

UNREGULATED

DC INPUT

D1 — Schottky, MBR360

L1 — 330µH, 415-0926 (AIE)

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

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

L

O

A

D

ON/OFF

COMPARATOR

FIXED GAIN

ERROR AMP

1 AMP

SWITCH

OUTPUT

DRIVER

+

-

+

-

VIN

FEED-

BACK

1.23V

BAND-GAP

REFERENCE

52 kHz

OSCILLATOR

RESET

THERMAL

SHUTDOWN

CURRENT

LIMIT

5

2

3

1

Note: Pin numbers are for the TO-220 package

INTERNAL

REGULATOR

ON/OFF

GND

ON/OFF

COMPARATOR

FIXED GAIN

ERROR AMP

1 AMP

SWITCH

OUTPUT

DRIVER

+

-

+

-

VIN

FEED-

BACK

1.23V

BAND-GAP

REFERENCE

52 kHz

OSCILLATOR

RESET

THERMAL

SHUTDOWN

CURRENT

LIMIT

5

2

3

1

4

INTERNAL

REGULATOR

ON/OFF

GND

3.1k

1.0k

4

Block Diagrams

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.

Switching Waveforms

10V

0

1A

0

1A

.5A

0

A

B

C

D

Load Transient Response

100µS/div.

+100mV

0

–100mV

Output

Voltage

Change

1.0A

0.5A

0

Output

Current

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

Fixed Regulator

Adjustable Regulator

Test Circuits and Layout Guidelines

Figure 1.