Internal

Regulator

ON/OFF

_

+

_

+

1.23-V

Band-Gap

Reference

52-kHz

Oscillator

Reset

Thermal

Shutdown

Current

Limit

FEEDBACK

7

CIN

+

VIN

6

Unregulated

DC Input

GND

5, 12, 13

OUTPUT

3

ON/OFF

9

COUT

+

D1

L

O

A

D

VOUT

1-A

Switch

Driver

Fixed-Gain

Error Amp

Comparator

R2

R1

R1 = Open, R2 = 0

Ω

L1

LM2575

www.ti.com

SLVS569F – JANUARY 2005 – REVISED AUGUST 2015

7 Detailed Description

7.1 Overview

The LM2575 provides all the active functions needed for a step-down (buck) switching regulator in an integrated

circuit. The wide input-voltage range is 4.75 V to 40 V. The output voltage is programmable by two external

resistors. No external frequency compensation is needed. The integrated switch is capable of delivering 1 A of

load current, with excellent line and load regulation. The fixed 52-kHz output has cycle-by-cycle current limiting,

and thermal shutdown. In addition, a manual shutdown is available through an external ON/OFF pin.

The LM2575 is characterized for operation over the virtual junction temperature range of –40°C to 125°C.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Feedback Connection

FEEDBACK must be connected between the two programming resistors. Again, both of these resistors must be

in close proximity to the regulator, and each must be less than 100 k

Ω to minimize noise pickup.

7.3.2 ON/OFF Input

ON/OFF should be grounded or be a low-level TTL voltage (typically < 1.6 V) for normal operation. To shut down

the LM2575 device and place in standby mode, a high-level TTL or CMOS voltage should be supplied to this pin.

ON/OFF must not be left open and safely can be pulled up to VIN with or without a pullup resistor.

7.3.3 Fault Protection

In the event of an output short or an overload condition, self-protection features lower the oscillator frequency to

approximately 18 kHz and the minimum duty cycle from 5% to approximately 2%. The resulting output voltage

drops to approximately 40% of its nominal value, causing the average power dissipated by the IC to lower.

Copyright © 2005–2015, Texas Instruments Incorporated

Submit Documentation Feedback

7

Product Folder Links: LM2575