DC1274A - ANALOG DEVICES - Datasheet.Wiki

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DEMO MANUAL DC1274A

DESCRIPTION

LTM8040

36V, 1A Step-Down

µModule LED Driver

Demo circuit DC1274A features the LTM

8040 36V, 1A

step-down constant current μModule

LED driver. The

demonstration circuit is designed to drive a single LED

or string of LEDs at up to 1A from a wide input voltage

range. The maximum LED string voltage is 13V and the

minimum voltage varies depending upon the BIAS pin sup-

ply arrangement. The demonstration circuit is assembled

with the BIAS pin connected to the LEDA pin.

The LTM8040 runs at 500kHz switching frequency by

default. DC1274A can be adjusted to raise the switching L, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of

Linear Technology Corporation. All other trademarks are the property of their respective owners.

PERFORMANCE SUMMARY

BOARD PHOTO

frequency, lower the LED current, and implement PWM

dimming. The shutdown feature can be examined by con-

necting the shutdown terminal to ground. The LTM8040

data sheet must be read in conjunction with this demo

manual prior to working on or modifying demo circuit

DC1274A.

Design files for this circuit board are available at

http://www.linear.com/demo

(TA = 25°C)

PARAMETER CONDITIONS/NOTES VALUE

Input Voltage Range ILED = 1A, VLEDA = 3.3V 4V to 36V

Output Current (ILED) R3 = Open 1A

Switching Frequency R2 = Open 500kHz

Maximum Output Voltage (VLEDA), Open LED Voltage 13V

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DEMO MANUAL DC1274A

QUICK START PROCEDURE

DC1274A is an easy way to evaluate the LTM8040. Refer

to the test procedures outlined below and Figure 1.

1. Make sure the power supply is less than 36V. With the

supply OFF, connect it to the VIN and GND terminals.

2. Connect an LED or string of LEDs between the LEDA

terminal and the GND terminal. For PWM dimming, the

PWM dimming MOSFET must be added to the PCB and

the string of LEDs must be attached between LEDA and

LED- terminals. However, for simplicity, the MOSFET is

not assembled on the board as shipped.

3. Turn on the input power supply and set the voltage

between 4V and 36V based on the forward voltage of

the LED(s) and desired output current. Please see the

LTM8040 data sheet for details.

4. Tie the shutdown terminal to ground in order to turn

the output off and examine the shutdown operation.

Allow the IC to run by releasing the shutdown terminal

connection to ground. The IC will run with the 100k

pull-up resistor from the shutdown terminal to VIN.

For LEDs or LED strings with a low forward voltage such

as a single red LED, the BIAS terminal can be disconnected

from the output (LPWR) and tied to the input (VIN). There

is a small trace on the back of the PCB (layer 4) that can

be cut in order to disconnect LPWR from BIAS. Please see

the LTM8040 data sheet for details regarding the proper

connection of the BIAS pin.

dc1274af

DEMO MANUAL DC1274A

QUICK START PROCEDURE

Figure 1. Proper Measurement Equipment Setup

–

–+

SHDN

OPTION

+–

OUTPUT CURRENT (mA)

EFFICIENCY (%)

400 800 1000

200 600

24VIN

12VIN

5VIN

Figure 2. Efficiency with Single 3.3VF LED at 1A. LED Current is Adjusted with ADJ Voltage

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DEMO MANUAL DC1274A

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 1 C1 CAP, 1210 2.2μF 10% 50V X7R TDK C3225X7R1H225K

2 1 R1 RES, 0402 100k 5% 1/16W VISHAY CRCW0402100KJNED

3 1 U1 IC, MODULE LINEAR TECH. LTM8040EV

Optional Demo Circuit Components

1 0 C2 CAP, 0805 OPT OPT

2 0 Q1 N-CHANNEL MOSFET, SOT-23 OPT OPT

3 0 R2, R3 RES, 0402 OPT OPT

Hardware

1 10 E1-E10 TURRET MILL-MAX 2501-2-00-80-00-00-07-0

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DEMO MANUAL DC1274A

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

SCHEMATIC DIAGRAM

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DEMO MANUAL DC1274A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

LT 0711 • PRINTED IN USA

DEMONSTRATION BOARD IMPORTANT NOTICE

Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:

This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT

OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete

in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety

measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union

directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.

If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date

of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU

OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS

FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR

ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.

The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims

arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all

appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or

agency certified (FCC, UL, CE, etc.).

No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,

customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.

LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.

Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and

observe good laboratory practice standards. Common sense is encouraged.

This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC applica-

tion engineer.

Mailing Address:

Linear Technology

1630 McCarthy Blvd.

Milpitas, CA 95035