Linear Technology DC1470A Quick setup guide

dc1470af

DEMO MANUAL DC1470A

DESCRIPTION

LT3743 High Current

Synchronous Step-Down LED

Driver with Three-State Control

Demonstrationcircuit1470Aisahighcurrentsynchronous

step-down LED driver with three-state control featuring

the LT

3743EUFD. The demo board is optimized for 20A

output from a 12V input. Being an LED driver, the output

current is being regulated until the output voltage reaches

a programmed voltage limit. This voltage limit on this

demo board is set to around 6V by R5 and R6. The 6V is

chosen because of the 6.3V voltage rating of the output

capacitors. The ideal load to be used with this demo board

is a single LED, such as PT120 from Luminus Devices.

Smaller LEDs may not be able to handle the high current,

even for a short period of time. At 20A, the demo circuit can

operate continuously. However, it is necessary to mount

the LED load on a proper heat sink and possibly with a

fan to avoid exceeding its maximum temperate rating.

Note: The DC470A will drive a LED with its cathode

grounded.GroundingcathodeoftheLED allows customers

to use positive input supply.

The input voltage range of the LT3743 itself is 6Vto 36V.

However,the demo board utilizes 30VMOSFETsto demon-

strate best efficiency so the maximum recommended input

voltage is 24V for the demo board. When input is above

20V during PWM dimming, a slightly larger inductance L, LT, LTC, LTM, 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

may be needed. The typical efficiency of the demo board

is 94% from a 12V input to 5V, 20A load. The lower the

input voltage, the higher the efficiency tends to be with

a given load. At output power level of 100W, a couple of

percent of efficiency improvement is a huge advantage in

minimizing temperature rise. If an efficiency measurement

is needed in an application, the output voltage must be

measured at the output capacitors instead of at the LED

load. This prevents cable loss from being counted as a

loss of the board. If efficiency measurement is required

during PWM dimming, the average current and voltage

values should be measured with proper equipment. All

LT3743 circuits turn off unnecessary circuits during PWM

off period to minimize power losses. As a result, efficiency

in many PWM dimming applications is almost the same

as efficiency of the constant current applications.

The DC1470A uses a split output capacitor configuration

to achieve <2μs current rise time from 0A to 20A. To see

the real rise time, connecting wires between the LED and

the board should be minimized to no more than 2 inches

Specifications are at TA= 25°C

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

PVIN* Input Supply Range, PVIN = VIN L1 is Optimized for 12V 12 26.4 V

VOUT* Output Voltage With One PT120 LED, 6V is the Over

Voltage Limit

4.5 6 V

IOUT Output Current CTRL_SEL > 1V 18.8 20 21.2 A

fSW Switching Frequency 400 430 460 kHz

IRISE Current Rise Time Following a PWM Rising Edge 2 μs

EFF Efficiency at DC VIN = 12V, VOUT = 5V, IOUT = 20A 94 %

*PVIN and VIN of the demo circuit are limited to 24V typical by the selection of MOSFETs. The LT3743 input range is 6V to 36V. VOUT maximum of the

demo circuit is limited to 6V due to the selection of the output capacitors.

Design files for this circuit board are available at

http://www.linear.com/demo/DC1470A

dc1470af

DEMO MANUAL DC1470A

total to minimize the wire inductance. 1-inch is even better.

The cathode of the LED should return to LED– with R25

populated with a resistor in a few mΩ. It is recommended

to measure the voltage on R25 with a short 50Ω coax

cable directly into a BNC connector on the oscilloscope.

The current can then be calculated from the measured

voltage. To get accurate current, R25 should be measured

before it is mounted on the board. A current probe adds

more delays to the rise time so using a current probe is

not recommended. If fast rise time measurement is not

necessary, the cathode of the LED can be connected to

GND as shown in Figure 1.

R27 can be used to slow down the gate drive. Slower gate

drive helps to reduce ringing on the SW node without

noticeable effect on the efficiency. A 10Ω is usually more

than enough to completely damp any ringing.

DESCRIPTION

Demonstration circuit 1470A is easy to set up to evalu-

ate the performance of the LT3743. Refer to Figure 1 for

proper measurement equipment setup and follow the

procedure below:

1. With power off, connect the input power supply to PVIN

and GND. The input power supply should have a current

limit of 10A or more.

2. With power off, connect a LED between VOUT and GND

or between VOUT and LED–, if fast rise time is to be

verified. When returning LED to LED–, R25 needs to

be populated. To check voltage across R25, the best

set up is to solder a short 50Ω coax cable across R25.

Connect the other end of the cable directly into a BNC

connector on an oscilloscope. A less perfect but easier

set up is to touch the probe tip directly across the IS+

and IS– terminals with out the probe ground wire. See

Figure 2 for setup. The latter set up tends to have more

noise but is ok for non-critical measurements. The LED

connecting wires should be as short as possible, 1 inch

total being ideal.

3. Turn on the power at the input.

R15, R16 and C15 help filtering out voltage spikes seen

on the SENSE+or SENSE–pin. It is critical to have those

components on a board.

The LT3743 has a three-state control. It can change output

current among zero, a low level and a high level, all in a

few μs. The low current level of the demo board is set to

around 5A. The high current level is 20A. Both levels can

be adjusted by changing the voltage dividers on CTRL_H

and CTRL_L. Applying a PWM signal to CTRL_SEL will

toggletheoutputbetween 5Ato 20A. While applying a PWM

signal to the PWM pin will toggle the output between either

0A to 5A or 0A to 20A depending on the CTRL_SEL level.

The LT3743 data sheet gives a complete description of

the part, operation and application information. The data

sheet must be read in conjunction with this demo manual

for DC1470A.

QUICK START PROCEDURE

4. At this time, the output current will be slightly below

5A. If no output current is observed, turn off PVIN and

check the connections.

5. To increase the load current to 20A, turn off PVIN. Pull

CTRL_SEL high either by populating R21 or by using an

external voltage source. Make sure the load can handle

20A continuously and the load voltage is not too high

for the board. Then turn on PVIN.

6. Both the low current level, 5A and the high current

level 20A can be adjusted by changing the voltage on

CTRL_L and CTRL_H terminals between 0V and 2V.

7. To evaluate the transient between 0A and a non-zero

current level, apply a PWM signal to the PWM terminal.

The nonzero current level is dictated by the CTRL_SEL

and CTRL_H or CTRL_L voltages.

8. To evaluate the transient between two non-zero cur rent

levels, apply a PWM signal to the CTRL_SEL terminal.

9. To modify the demo board for other applications, please

contact Linear Applications Group for help.

dc1470af

DEMO MANUAL DC1470A

QUICK START PROCEDURE

Figure 1. Proper Measurement Equipment Setup

Figure 2. Measuring Voltage Across R25

IS–

IS+

dc1470af

DEMO MANUAL DC1470A

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 4 C1, C12, C16, C17 CAP., X7R, 4.7μF, 50V, 10%, 1210 MURATA, GRM32ER71H475KA88L

2 1 C2 CAP., X7R, 1μF, 50V, 10%,0805 MURATA, GRM21BR71H105KA12L

3 1 C3 CAP., X7R, 0.22μF, 10V,10%,0603 MURATA, GRM188R71A224KA01D

4 1 C4 CAP., X5R, 22μF, 6.3V, 20%, 0805 MURATA, GRM21BR60J226ME39L

5 6 C5, C6, C18, C21, C23, C25 CAP., POSCAP, 470μF, 6.3V, D4D PANSONIC, 6TPF470MAH

6 1 C7 CAP., C0G, 2nF, 50V, 0603 MURATA, GRM1885C1H202JA01

7 1 C8 CAP., X7R, 1μF, 16V, 10%,0603 MURATA, GRM188R71C105KA12D

8 2 C9,C10 CAP., C0G, 5600pF, 50V, 5% 0603 MURATA, GRM1885C1H562JA01D

9 1 C11 CAP., ALUM., ELECT., 100μF, 50V SUN ELECTRONICS., 50CE100LX

10 1 C15 CAP., X5R, 0.033μF, 50V, 0603 AVX, 06035D333KAT2A

11 1 C26 CAP., X7R, 1200pF, 50V,5%, 0603 AVX, 06035C122JAT2A

12 1 C27 CAP., X7R, 10μF, 25V,10%,1206 MURATA, GRM31CR71E106KA12L

13 1 D1 SCHOTTKY RECTIFIER, 40V, SOD523 NXP SEMI., PMEG4002EB,115

14 1 D2 2.0A LOW VF SCHOTTKY RECTIFIER DIODES INC., DFLS240L-7

15 1 L1 INDUCTOR, 1.3μH WURTH ELECTRONICS, 7443551130

16 2 Q1,Q2 N-CHANNEL MOSFET, LFPAK INFINEON, BSC080N03LS G

17 1 Q3 N-CHANNEL MOSFET, LFPAK INFINEON, BSC011N03LSI

18 2 Q5,Q6 MOSFET, 40V, DUAL N-CHANEL, PPAK VISHAY, Si7234DP

19 1 R1 RES., CHIP, 124k, 1%, 1/W, 0603 VISHAY, CRCW0603124KFKEA

20 1 R2 RES., CHIP, 374k, 1%, 1/W, 0603 VISHAY, CRCW0603374KFKEA

21 1 R3 RES., CHIP, 0.0025Ω, 1W, 1%, 2512 VISHAY, WSL25122L500FEA

22 7 R4, R9, R10, R12, R13, R14, R20 RES., CHIP, 100k, 1%, 1/W, 0603 VISHAY, CRCW0603100KFKEA

23 3 R5, R7, R8 RES., CHIP, 51k, 1%, 1/W, 0603 VISHAY, CRCW060351K0FKEA

24 1 R6 RES., CHIP, 10k, 1%, 1/W, 0603 VISHAY, CRCW060310K0FKEA

25 2 R15, R16 RES., CHIP, 10Ω, 1%, 1/W, 0603 VISHAY, CRCW060310R0FKEA

26 1 R18 RES., CHIP, 24.9k, 1%, 1/W, 0603 VISHAY, CRCW060324K9FKEA

27 1 R19 RES., CHIP, 432k, 1%, 1/W, 0603 VISHAY, CRCW0603432KFKEA

28 1 R23 RES., CHIP, 3.01k, 1%, 1/W, 0603 VISHAY, CRCW06033K01FKEA

29 1 R24 RES., CHIP, 2k, 1%, 1/W, 0603 VISHAY, CRCW06032K00FKEA

30 1 U1 I.C. LT3743EUFD, 28-PIN QFN-4×5 LINEAR TECH., LT3743EUFD#PBF

Additional Demo Board Circuit Components

1 0 C13, C14, C19, C20, C22, C24 CAP., D4D, OPT

2 0 R11, R21, R22, R26 RES., OPT, 0603 VISHAY, CRCW06030000Z0EA

3 2 R17, R27 RES., CHIP, 0Ω, 0603

4 0 R25 RES., CHIP, 2512, OPT

5 0 Q4 OPT

Hardware for Demo Board Only

1 10 E1-E8, E13, E14 TURRET, TESTPOINT, 091" MILL MAX 2501-2-00-80-00-00-07-0

2 4 E9-E12 JACK BANANA KEYSTONE, 575-4

3 4 STAND-OFF STAND-OFF, NYLON 0.5" TALL KEYSTONE, 8833(SNAP ON)

dc1470af

DEMO MANUAL DC1470A

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

D D

C C

B B

A A

6V - 36V

(400kHz)

HIGH CURRENT SYNCHRONOUS

* See Quick Start Guide

VIN

VCC_INT

VIN

VCC_INT

REVISION HISTORY

DESCRIPTION DATEAPPROVEDECO REV

WALKER B.PRODUCTION13 10-02-09

REVISION HISTORY

DESCRIPTION DATEAPPROVEDECO REV

WALKER B.PRODUCTION13 10-02-09

REVISION HISTORY

DESCRIPTION DATEAPPROVEDECO REV

WALKER B.PRODUCTION13 10-02-09

SIZE

DATE:

IC NO.

REV

SHEET OF

TITLE:

CONTRACT NO.

APPROVALS

PCB DES.

ENG.

TECHNOLOGY Fax: (408)434-0507

Milpitas, CA 95035

Phone: (408)432-1900

1630 McCarthy Blvd.

LTC Confidential-For Customer Use Only

CUSTOMER NOTICE

LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A

CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;

HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO

VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL

APPLICATION. COMPONENT SUBSTITUTION AND PRINTED

CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT

PERFORMANCE OR RELIABILITY. CONTACT LINEAR

TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.

THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.

SCHEMATIC

Friday, July 31, 2015

STEP-DOWN LED DRIVER WITH THREE-STATE CONTROL

ANTONINA K.

WALKER B.

LT3743EUFD

DEMO CIRCUIT 1470A

SIZE

DATE:

IC NO.

REV

SHEET OF

TITLE:

CONTRACT NO.

APPROVALS

PCB DES.

ENG.

TECHNOLOGY Fax: (408)434-0507

Milpitas, CA 95035

Phone: (408)432-1900

1630 McCarthy Blvd.

LTC Confidential-For Customer Use Only

CUSTOMER NOTICE

LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A

CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;

HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO

VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL

APPLICATION. COMPONENT SUBSTITUTION AND PRINTED

CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT

PERFORMANCE OR RELIABILITY. CONTACT LINEAR

TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.

THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.

SCHEMATIC

Friday, July 31, 2015

STEP-DOWN LED DRIVER WITH THREE-STATE CONTROL

ANTONINA K.

WALKER B.

LT3743EUFD

DEMO CIRCUIT 1470A

SIZE

DATE:

IC NO.

REV

SHEET OF

TITLE:

CONTRACT NO.

APPROVALS

PCB DES.

ENG.

TECHNOLOGY Fax: (408)434-0507

Milpitas, CA 95035

Phone: (408)432-1900

1630 McCarthy Blvd.

LTC Confidential-For Customer Use Only

CUSTOMER NOTICE

LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A

CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;

HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO

VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL

APPLICATION. COMPONENT SUBSTITUTION AND PRINTED

CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT

PERFORMANCE OR RELIABILITY. CONTACT LINEAR

TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.

THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.

SCHEMATIC

Friday, July 31, 2015

STEP-DOWN LED DRIVER WITH THREE-STATE CONTROL

ANTONINA K.

WALKER B.

LT3743EUFD

DEMO CIRCUIT 1470A

CTRL_L

E12

GND

C26

1.2nF

C18

470uF

10k

C25

470uF

4.7uF

R19

432K

R23

3.01K

R15 10

51K

374K

BSC080N03LS G

1uF

C14

OPT

BSC011N03LSI

R17 0

51K

124K

R27

CTRL_SEL

Si7234DP

VIN

R21

OPT

LT3743EUFD

EN/UVLO

VREF

CTRL_T

CTRL_H

CTRL_L

GND

SENSE+ 11

SENSE- 12

VCL 13

VCH 14

SYNC

CTRL_SEL

PWM

PWMGH 19

PWMGL 22

HG 23

SW 24

CBOOT 25

LG 26

VCC_INT 27

VIN

GND

PMEG4002EB

1 2

C23

470uF

C15

33nF

E13

IS+

R26

OPT

R20

100K

R16 10

C16

4.7uF

E11

LED-

C21

470uF

SYNC

0.0025

DFLS240

OPT

R10

100K

1.3uH

C27

10uF

R22

OPT

R11

OPT

E14

IS-

R13

100K

R4 100K

C11

100uf,50V

50CE100LX

100K

R24

51K

CTRL_H

C24

OPT

C19

OPT

C13

OPT

C17

PVIN

6V - 36V

R25

OPT

5.6nF

C22

OPT

22uF

6.3V

470uF

2nF

R18

24.9K

PWM Q6

Si7234DP

EN/UVLO

R12

100K

C12

C20

OPT

E10

VOUT

OPT

R14

100K

1uF

50V

0.22uF

GND

470uF

C10

5.6nF

dc1470af

DEMO MANUAL DC1470A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

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

 LINEAR TECHNOLOGY CORPORATION 2015

LT 0915 • 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 application

engineer.

Mailing Address:

Linear Technology

1630 McCarthy Blvd.

Milpitas, CA 95035

Mouser Electronics

Authorized Distributor

Click to View Pricing, Inventory, Delivery & Lifecycle Information:

Analog Devices Inc.:

DC1470A

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