Linear Technology DC2257A Quick setup guide

dc2257af

DEMO MANUAL DC2257A

DESCRIPTION

LTM8005

38VIN, 38VOUT Boost µModule

LED Driver with 40V Switch

Demonstration circuit 2257A features the LT M

8005 – a

38VIN, 38VOUT boost μModule

LED driver that can dis-

connect the output to protect against faults and provides

spread spectrum switching to simplify emissions compli-

ance. DC2257A is an LED driver with an input range for

normal operation from 6Vto27V. OVLO becomes active for

inputs above 29V and the maximum input voltage is 38V.

The LED current is 1.2A and the base switching frequency

is 350kHz. The efficiency is 92% when the input is 12V

with a 35V LED load. 35V is the maximum LED voltage.

The demo circuit requires application of an external voltage

to the PWM terminal for operation. The external voltage

can be a DC level or an appropriate PWM dimming signal.

Common frequencies for PWM dimming are 100Hz or

higher. Analog dimming is achieved using the CTRL inputs.

DC2257A allows adjustments to output voltage, output

current, input current, switching frequency, frequency L, LT, LTC, LTM, Linear Technology, the Linear logo and μModule are registered trademarks of

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

BOARD PHOTO

modulation rate including disable, feedback loop com-

pensation, EN/UVLO threshold, OVLO threshold, soft-

start period, and fault latch-off or hiccup. In most cases,

adjustment is made by modifying the appropriate resistor

or capacitor component(s).

DC2257A provides outputs for input and output current

monitoring and fault status for short and open LEDs.

The demo circuit is designed to be easily reconfigured

to buck mode, buck-boost mode and SEPIC topologies.

There are placeholders to mount optional LC input filter

components.

The LTM8005 data sheet must be read in conjunction with

this demo manual to properly use or modify DC2257A.

Design files for this circuit board are available at

http://www.linear.com/demo/DC2257A

dc2257af

DEMO MANUAL DC2257A

QUICK START PROCEDURE

PARAMETER CONDITIONS MIN TYP MAX

Minimum Input Voltage, VPVIN 6V

Maximum Input Voltage – Switching, VPVIN 27V

Maximum Input Voltage – Not Switching, VPVIN VOVLO ≥ 1.25 38V

Maximum LED Voltage, VLED 35V

LED Current, ILED R5 = 100k, R6 = 73.2k 1.2A

Input Turn-On Voltage, VPVIN(EN) R7 = 19.1k, R8 = 1M, R9 = 93.1k, VPVIN Rising 5.9V

Input Turn-Off Voltage, VPVIN(UVLO) R7 = 19.1k, R8 =1M, R9 = 93.1k, VPVIN Falling 4.9V

Input OVLO Turn-Off Voltage, VPVIN(OVLO_TURN-OFF) R7 = 19.1k, R8 = 1M, R9 = 93.1k, VPVIN Rising 29.1V

Input OVLO Turn-On Voltage, VPVIN(OVLO_TURN-ON) R7 = 19.1k, R8 = 1M, R9 = 93.1k, VPVIN Falling 28.4V

Efficiency VPVIN = 12V, VLED = 35V, ILED = 1.2A 92%

Switching Frequency R1 = 23.2k, Spread Spectrum = OFF 350kHz

Input Current Limit RS1 = 0.008Ω 7.5A Peak

PERFORMANCE SUMMARY

Specifications are at TA= 25°C

To use DC2257A to evaluate the performance of the

LTM8005, refer to Figure 1 for the proper measurement

equipment setup and then follow the procedure below.

NOTE: PWM must be pulled high to work. If PWM is not

used, connect the PWM terminal to a 2V to 5V source or

connect the PWM pin to VREF on the PCB using R18.

1. Connect a string of LEDs with a forward voltage of 35V

or less, but greater than the PVIN voltage, to the LED+

and GND terminals on the PCB as shown in Figure 1.

2. Connect the EN/UVLO terminal to ground with a

clip-onlead.

3. With the power off, connect the input power supply to

the PVIN and GND terminals within the voltage range

specified on the PCB. Make sure that the input power

supply voltage does not exceed the forward voltage of

the LED string. OVLO becomes active to inhibit switch-

ing for an input voltage of greater than 29V.

4. Connect an input to the PWM terminal. If PWM is not

used, connect PWM to a 2V to 5V DC source or to VREF

on the PCB using resistor R18. PWM must be pulled

high to work. For PWM dimming, connect a 100Hz or

higher PWM signal to the PWM terminal.

5. Turn the PVIN power supply on.

6. Release the EN/UVLO to GND connection.

7. Observe the LED string running at the programmed

LED current;or, observe the reduction of brightness

in the LED string with PWM dimming.

dc2257af

DEMO MANUAL DC2257A

Figure 1. Proper Measurement Equipment Setup

QUICK START PROCEDURE

dc2257af

DEMO MANUAL DC2257A

Figure 2. Output Current Noise Spectrum with Spread Spectrum = OFF, VIN = 12V, POUT = 42W, CT-1 Current Transformer

Figure 3. Output Current Noise Spectrum with Spread Spectrum = ON, VIN = 12V, POUT = 42W, CT-1 Current Transformer

QUICK START PROCEDURE

DETECTOR = PEAK–HOLD

RBW = 9kHz

CT–1 CURRENT TRANSFORMER

SPREAD SPECTRUM = OFF

FREQUENCY (MHz)

–50

–40

–30

–20

–10

AMPLITUDE (dBµV)

Output Current Noise Spectrum

DC2257A F02

DETECTOR = PEAK–HOLD

RBW = 9kHz

CT–1 CURRENT TRANSFORMER

SPREAD SPECTRUM = ON

FREQUENCY (MHz)

–50

–40

–30

–20

–10

AMPLITUDE (dBµV)

DC2257A F02

dc2257af

DEMO MANUAL DC2257A

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 1 C1 CAP., X7R, 1μF, 50V, 10%, 0805 MURATA, GRM21BR71H105KA12L

2 5 C2, C3, C4, C7, C8 CAP., X7R, 4.7μF, 50V, 10%, 1210 MURATA, GRM32ER71H475KA88L

3 1 C5 CAP., X7R, 0.022μF, 16V, 10%, 0603 MURATA, GRM188R71C223KA01D

4 1 C6 CAP., X7R, 0.1μF, 25V, 10%, 0603 AVX, 06033C104KAT2A

5 1 L1 INDUCTOR, 10μH COILCRAFT, XAL8080-103ME

6 1 R1 RES, CHIP, 23.2k, 1/10W, 1%, 0603 VISHAY, CRCW060323K2FKEA

7 1 R2 RES, CHIP, 12.4k, 1/10W, 1%, 0603 VISHAY, CRCW060312K4FKEA

8 1 R3 RES, CHIP, 1.5k, 1/10W, 5%, 0603 VISHAY, CRCW06031K50JNEA

9 1 R4 RES, CHIP, 374k, 1/10W, 1%, 0603 VISHAY, CRCW0603374KFKEA

10 1 R5 RES, CHIP, 100k, 1/10W, 1%, 0603 VISHAY, CRCW0603100KFKEA

11 1 R6 RES, CHIP, 73.2k, 1/10W, 1%, 0603 VISHAY, CRCW060373K2FKEA

12 1 U1 I.C., μMODULE LED DRIVER, 80-BGA LINEAR TECH, LTM8005EY#PBF

Optional Demo Circuit Components

1 1 C13 CAP., X7R, 0.1μF, 25V, 10%, 0603 AVX, 06033C104KAT2A

2 0 C11, C19, C27 (OPT) CAP., 0603

3 0 C9, C10, C12, C15-C18, C22-C26 (OPT) CAP., 1210

4 1 C14 CAP., X7R, 6.8nF, 16V, 10%, 0603 AVX, 0603YC682KAT2A

5 0 C21 (OPT) CAP., ALUM, OPT, 10mm DIA.

6 1 D1 DIODE, SMA FAIRCHILD SEMI.,ES1A

7 0 L2 (OPT) INDUCTOR, OPT, 8mm × 8mm

8 0 M1 (OPT) MOSFET, SOT23

9 0 Q1 (OPT) TRANS, SOT23

10 1 RS1 RES, CHIP, .008Ω, 1W, 1%, 2512 VISHAY, WSL25128L000FEA

11 0 RS2 (OPT) RES, 2010

12 1 R7 RES, CHIP, 19.1k, 1/10W, 1%, 0603 VISHAY, CRCW060319K1FKEA

13 1 R8 RES, CHIP, 1M, 1/10W, 1%, 0603 VISHAY, CRCW06031M00FKEA

14 1 R9 RES, CHIP, 93.1k, 1/10W, 1%, 0603 VISHAY, CRCW060393K1FKEA

15 0 R10, R12-R15, R18, R19, R21-R27, R30 (OPT) RES, 0603

16 1 R11 RES, CHIP, 0, 1/10W, 1%, 0603 VISHAY, CRCW06030000Z0EA

17 1 R16 RES, CHIP, 0, 1/4W, 1%, 1206 VISHAY, CRCW12060000Z0EAHP

18 0 R20 (OPT) RES, 1206

19 3 R17, R28, R29 RES, CHIP, 100k, 1/10W, 5%, 0603 VISHAY, CRCW0603100KJNEA

Hardware

1 19 E1-E19 TESTPOINT, TURRET, .094" PBF MILL-MAX, 2501-2-00-80-00-00-07-0

2 1 JP1 HEADER 3-PIN 0.079 SINGLE ROW WURTH, 620 003 111 21

3 1 XJP1 SHUNT, .079" CENTER WURTH, 608 002 134 21

dc2257af

DEMO MANUAL DC2257A

NOTE: UNLESS OTHERWISE SPECIFIED.

1. ALL RESISTORS 5%, 0603.

2. ALL CAPACITORS 0603.

SPREAD SPECTRUM

PVIN

VOUTPVIN

IVINN

VOUT

ISN

EN/UVLO

VIN

VREF

CTRL1 CTRL2

PWM

/OPENLED

OVLO

19.1k

LTM8005EY

VIN

EN/UVLO

ISMON

VREF

PWM

RAMP

CTRL1

CTRL2

DA A5

DA A6

VOUT A7

VOUT A8

DA B5

DA B6

VOUT B7

VOUT B8

DA C5

DA C6

VOUT C7

VOUT C8

ISN F6

ISN F7

ISN F8

LED+ G6

LED+ G7

LED+ G8

IVINCOMP H2

SHORTLED H7

OPENLED H8

AUX J2

FB K2

VC K3

SW A1

SW A2

SW A3

SW A4

SW B1

SW B2

SW B3

SW B4

SW C1

SW C2

SW C3

SW C4

IVINN F2

IVINP G2

OVLO H1

GND

100k

4.7uF

50V

1210

0.1uF

R29

100k

E14

GND

R12

(OPT)

E11

VOUT

C12

(OPT)

1210

C11

(OPT)

1.5k

E10

GND

R11

0 Ohm

4.7uF

50V

1210

4.7uF

50V

1210

RS1

0.008

2512

GND

1uF

50V

0805

CTRL2

PVIN

6V - 27V

38V MAX.

29V OVLO

E18

GND

CTRL1

23.2k

350kHz

4.7uF

50V

1210

E17

OPENLED

E19

V_EXT

12.4k

R17

100k

C13

0.1uF

E15

IVINCOMP

10uH

COILCRAFT

XAL8080-103ME

VIN

6V - 27V

38V MAX.

29V OVLO

374k

ISMON

JP1

OFF

73.2k

C10

(OPT)

1210

EN/UVLO

22nF

ES1A

4.7uF

50V

1210

PWM

E13

GND

C14

6.8nF

E16

SHORTLED

93.1k

R22

(OPT)

R28

100k

C19

(OPT)

E12 LED+

1.2A

35V LED MAX.

R16

0 Ohm

1206

(OPT)

1210

SCHEMATIC DIAGRAM

dc2257af

DEMO MANUAL DC2257A

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

IVINN

VOUT PVIN

VOUT

PVIN

VOUT

VREF

VIN

CTRL1

PWM

/OPENLED

EN/UVLO

OVLO

ISN

C17

(OPT)

1210

R26

(OPT)

C26

(OPT)

1210

R27

(OPT)

C18

(OPT)

1210

C23

(OPT)

1210

C25

(OPT)

1210

SOT23

(OPT)

R24

(OPT)

R19

(OPT)

C16

(OPT)

1210

C24

(OPT)

1210

RS2

(OPT)

2010

C22

(OPT)

1210

R25

(OPT)

R23

(OPT)

C15

(OPT)

1210

C27

(OPT)

R13

(OPT)

SOT23

R21

(OPT)

8mm x 8mm

C21

10mmDia.SMD

(OPT)

R18

(OPT)

R10

(OPT)

R14

(OPT)

R15

(OPT)

R30

(OPT)

R20

1206

(OPT)

dc2257af

DEMO MANUAL DC2257A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

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

LT 1016 • 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

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