Linear Technology LT1374CFE Manuel utilisateur

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 474

4A, 500KHZ STEP DOWN SWITCHING REGULATOR

LT1374CFE

DESCRIPTION

Demonstration circuit 474 is a step-

down buck regulator using the

LT1374CFE 500kHz-switching regulator.

The high switching frequency allows

the use of small inductors and filter

components, making this circuit ideal

for space conscious systems.

0.8

0.85

0.9

0.95

012345

Load Current

Efficiency

Figure 1. Efficiency, 10V V

, 5V V

OUT

Figure 1 shows efficiency versus load

for a typical application. The best

efficiency is realized with a load

current between 700mA and 2 amps.

Full load efficiency is 87%. The

maximum allowed die temperature is

125°C. Figure 2 shows die temperature

vs. output load current with V

12V. At full load the die temperature

rise is 70°C indicating that the demo

is suitable for ambient temperatures

of up to 125°C – 70°C = 55°C.

0123

Load (Amps)

Tem perature (Degrees C)

Figure 2. Die Temperature vs Output

Current, V

= 12V

QUICK START PROCEDURE

Refer to Figure 3 for proper measure-

ment equipment setup and follow the

procedure below:

Connect input power to the Vin and

GND terminals. V

should be be-

tween 5V and 25V. The power source

should be capable of delivering

25W.

NOTE:

5V output operation requires

a minimum V

of 6V

Connect the output load to the Vout

and GND terminals.

Select desired output voltage using

the voltage selecting jumper

NOTE:

Choose 3.3V operation by mov-

ing the voltage selection jumper to

the 3.3V position. Demonstration

circuit 474 is optimized for 5V op-

eration, and when operating at 3.3V

out, high V

and light load some

instability may arise. Increasing

the output capacitance removes this

instability. Use a 330µF, 4V, low

ESR cap such as the “Poscap” or

“Oscon”.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 474

4A, 500KHZ STEP DOWN SWITCHING REGULATOR

To turn the circuit off, ground the

terminal labeled SHDN

To test the synchronization feature

of the demo board apply a sync sig-

nal to the sync terminal and note

the shift in the operating fre-

quency. The Sync signal should have

an amplitude greater than 2.2V,

duty cycle of between 10% and 90%

and a frequency of 580kHz–1000kHz

MEASUREMENT NOTES

Voltage measurements

The correct way to measure voltage is

at the terminal of the demo board.

Attempts to measure output voltage at

the load will result in a too low

output voltage due to wiring loss.

This is especially true at high cur-

rent. Needless to say any efficiency

calculation should be made using demo

circuit terminal voltages as opposed

to load or power source terminal

voltages.

Ripple Voltage Measurements

The ceramic capacitors used in this

demo board have almost no ESR and are

extremely effective filters. In order

to correctly measure output ripple

voltage correct technique is impor-

tant. The scope ground lead and

sheath should be removed and the out-

put ripple measured by placing the

scope probe directly across the out-

put Vout and GND pins as illustrated

in Figure 4.

5V TO 25V

SUPPLY

25W

–

–+

–

LOAD

Figure 3. Proper Measurement Equipment Setup

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 474

4A, 500KHZ STEP DOWN SWITCHING REGULATOR

VIN

GND

Figure 4. Scope Probe Placement for Measuring Output Ripple

Autres manuels Linear Technology Contrôleurs

Linear Technology

Linear Technology DC1669A Guide de configuration rapide

Linear Technology

Linear Technology DC2007A-B Guide de configuration rapide

Linear Technology

Linear Technology 1158A Manuel utilisateur

Linear Technology

Linear Technology DC1736A Guide de configuration rapide

Linear Technology

Linear Technology DC2087A Guide de configuration rapide

Linear Technology

Linear Technology LTM4616 Guide de configuration rapide

Linear Technology

Linear Technology DC1989A-A Guide de configuration rapide

Linear Technology

Linear Technology LTC3210-2 Manuel utilisateur

Linear Technology

Linear Technology LTC1736 Manuel utilisateur

Linear Technology

Linear Technology LTM4624EY Manuel utilisateur

Linear Technology

Linear Technology DC1477B Guide de configuration rapide

Linear Technology

Linear Technology LT3759 Guide de configuration rapide

Linear Technology

Linear Technology LT3480 Manuel utilisateur

Linear Technology

Linear Technology LTC4266A Manuel utilisateur

Linear Technology

Linear Technology DC1817B Guide de configuration rapide

Linear Technology

Linear Technology LT3507A Guide de configuration rapide

Linear Technology

Linear Technology LT3695 Series Manuel utilisateur

Linear Technology

Linear Technology DC2453A Guide de configuration rapide

Linear Technology

Linear Technology LT3790 Guide de configuration rapide

Linear Technology

Linear Technology LTM4650-1 Guide de configuration rapide

Linear Technology

Linear Technology LT8611 Manuel utilisateur

Linear Technology

Linear Technology 1215 Manuel utilisateur

Linear Technology

Linear Technology LTM8003 Guide de configuration rapide

Linear Technology

Linear Technology DC1588A Guide de configuration rapide

Manuels Contrôleurs populaires d'autres marques

Digiplex

Digiplex DGP-848 Mode d'emploi

YASKAWA

YASKAWA SGM series Manuel utilisateur

Sinope

Sinope Calypso RM3500ZB Manuel utilisateur

Isimet

Isimet DLA Series Style 2 Manuel d'installation

LSIS

LSIS sv-ip5a Manuel utilisateur

Rockwell Automation

Rockwell Automation 1769-L31 Manuel utilisateur

Airflow

Airflow Uno hab Manuel utilisateur

ABB

ABB ACS580-01 drives Manuel utilisateur

Panasonic

Panasonic GM1 Series Manuel utilisateur

Emerson

Emerson SW93 Manuel utilisateur

AutoAqua

AutoAqua Smart ATO micro SATO-120P Manuel utilisateur

Panasonic

Panasonic FP? Positioning Unit RTEX Manuel utilisateur

Samson

Samson Type 5824 Manuel de service

Alpha IP

Alpha IP MIOB 21001 Manuel utilisateur

Siemens

Siemens OpenAir GMA 1 Series Manuel utilisateur

Surecom

Surecom SR-629 Manuel utilisateur

Fishman

Fishman TriplePlay Manuel utilisateur

Regulus

Regulus SRS1 T Manuel utilisateur