LM25574BLDT National Semiconductor, LM25574BLDT Datasheet

LM25574BLDT

Manufacturer Part Number

LM25574BLDT

Description

WEBENCH BUILD IT BOARD LM25574

Manufacturer

National Semiconductor

Series

WEBENCH®, PowerWise®, SIMPLE SWITCHER®r

Datasheets

1.LM25574MTXNOPB.pdf (22 pages)

2.LM25574BLDT.pdf (4 pages)

Specifications of LM25574BLDT

Main Purpose

DC/DC, Step Down

Outputs And Type

1, Non-Isolated

Voltage - Output

1.23 ~ 40V

Current - Output

500mA

Voltage - Input

6 ~ 42V

Regulator Topology

Buck

Board Type

Partially Populated - Main IC Only

Utilized Ic / Part

LM25574

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

Power - Output

Frequency - Switching

Available stocks

Company

Part Number

Manufacturer

Quantity

Price

Company:

Bonase Electronics (HK) Co., Limited

Part Number:

LM25574BLDT

Manufacturer:

National Semiconductor

Quantity:

135

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Quick Start Guide for a 0.5

Amp Buck Regulator Using

The LM5574 and LM25574

The LM5574 and LM25574 switching regulators feature all of

the functions necessary to implement an efficient high voltage

buck regulator using a minimum of external components.

These easy to use regulators include either a 42V (LM25574)

or a 75V (LM5574) N-Channel buck switch with an output

current capability of 0.5 Amps. The operating frequency is

programmable from 50kHz up to 1MHz. Protection features

include: current limit, thermal shutdown and remote shutdown

capability. The device is available in a TSSOP-16 package.

This step-by-step guide provides an easy to use process to

quickly select the external components necessary to com-

Quick Guide Design Worksheet

Step 1. List the basic requirements:

Output Current: 0 to 0.5 Amp

Step 2. If the Input Voltage Max Spec [3] is less than 42V use

the LM25574. If the Input Voltage Max Spec [3] is greater than

42V but less than 75V use the LM5574. Both devices require

the Input Voltage Min Spec [2] to be greater than 6V.

Step 3. Selection of the operating frequency is a trade-off be-

tween the conversion efficiency and solution size. Operating

at a high frequency, with a relatively high input voltage will

severely impact the efficiency and consequently generate a

lot of heat. In some applications, the selection of a high op-

Output Voltage:

Input Voltage Min Spec:

Input Voltage Max Spec:

Selected Regulator:

V [1]

V [2]

V [3]

300034

[4]

FIGURE 1. Application Schematic

National Semiconductor

Application Note 1563

January 2007

plete a design. More detailed information including theory of

operation, design trade-offs and additional application guid-

ance is available in the device datasheet. Shown below in

Figure 1 is a complete schematic for a 0.5 Amp step-down

DC-DC converter. Several external component values can be

standardized for most applications. The input voltage range,

output voltage and desired operating frequency dictate the

remaining component values.

An Excel based spreadsheet derived from the guide is avail-

able on the National Semiconductor website.

erating frequency will limit the input voltage range. The rec-

ommended maximum operating frequency for applications

using LM5574 is 500 KHz. When using the LM25574 the op-

erating frequency may be set as high as 1MHz. Select a target

operating frequency from 50 kHz to 1MHz (500kHz for the

LM5574). Check to see if the Vin(min) limits the selected op-

erating frequency:

The selected operating frequency must be less than Fsw

(max) calculated above, if not reduce the operating frequen-

cy. Check to see if the Vin(max) limits the selected operating

frequency:

www.national.com

30003401

Related parts for LM25574BLDT

LM25574BLDT Summary of contents

Page 1

... An Excel based spreadsheet derived from the guide is avail- able on the National Semiconductor website. FIGURE 1. Application Schematic erating frequency will limit the input voltage range. The rec- ommended maximum operating frequency for applications using LM5574 is 500 KHz ...

Page 2

The selected operating frequency must be less than Fsw (max) calculated above, if not reduce the operating frequen- cy. Selected operating frequency Fsw: Step 4. Calculate the value of Rt for the selected operating frequency. Selected value for R1: Step ...

Page 3

SCH REF PART NUMBER C1 (Cin) C2 (Cout) C3 (CRAMP) C4 (Css) C2012X7R2A103K C5 (Ccomp) C6 (Cboot) C2012X7R2A223K C7 (Cbyp) C2012X7R1C474M (Rfb1) R2 (Rfb2) R3 (Rt) R4 (Rcomp) U1 DESCRIPTION VALUE INPUT CAPACITOR OUTPUT CAPACITOR RAMP CAPACITOR ...

Page 4

... National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other brand or product names may be trademarks or registered trademarks of their respective holders. ...

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