LM25574EVAL National Semiconductor, LM25574EVAL Datasheet
LM25574EVAL
Manufacturer Part Number
LM25574EVAL
Description
BOARD EVALUATION FOR LM25574
Manufacturer
National Semiconductor
Series
PowerWise®, SIMPLE SWITCHER®r
Specifications of LM25574EVAL
Main Purpose
DC/DC, Step Down
Outputs And Type
1, Non-Isolated
Voltage - Output
5V
Current - Output
500mA
Voltage - Input
7 ~ 42V
Regulator Topology
Buck
Frequency - Switching
300kHz
Board Type
Fully Populated
Utilized Ic / Part
LM25574
Lead Free Status / RoHS Status
Not applicable / Not applicable
Power - Output
-
Other names
*LM25574EVAL
© 2007 National Semiconductor Corporation
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 LM25574EVAL
Image
Part Number
Description
Manufacturer
Datasheet
Request
R
Part Number:
Description:
National Semiconductor [8-Bit D/A Converter]
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
National Semiconductor [Media Coprocessor]
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
Digitally Controlled Tone and Volume Circuit with Stereo Audio Power Amplifier, Microphone Preamp Stage and National 3D Sound
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
Digitally Controlled Tone and Volume Circuit with Stereo Audio Power Amplifier, Microphone Preamp Stage and National 3D Sound
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
AC97 Rev 2 Codec with Sample Rate Conversion and National 3D Sound
Manufacturer:
National Semiconductor
Part Number:
Description:
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
General Purpose, Low Voltage, Low Power, Rail-to-Rail Output Operational Amplifiers
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
8-bit 20 MSPS flash A/D converter.
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
Low Noise Quad Operational Amplifier
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
Quad Differential Line Receivers
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
Quad High Speed Trapezoidal? Bus Transceiver
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
Dual Line Receiver
Manufacturer:
National Semiconductor
Datasheet:
Part Number:
Description:
TTL to 10k ECL Level Translator with Latch
Manufacturer:
National Semiconductor
Datasheet:
LM25574EVAL 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. ...