Linear Technology DC1576 Guida rapida alla configurazione

dc1573af

DEMO MANUAL DC1573A

Description

LT3760

8-Channel 100mA

High Voltage LED Driver

DC1573A is an 8-Channel 100mA High Voltage LED Driver

featuring the LT

3760. The LT3760 drives up to 100mA

per string and has a maximum LED string voltage of 45V.

DC1573A is set at 1MHz switching frequency for smallest

inductor and capacitor size as well as maximum PWM

dimming performance. Overvoltage protection is set at

55V in case the LEDs are removed from the circuit. If the

LEDs are opened, the FAULT terminal output flag goes

low and reports the fault condition. The VIN terminal is

powered from 10V to 14V input separated from the 24V

PVIN supply for best thermal performance. If one or more

of the 8 LED channels is not used, its LED pin or terminal

should be tied to LED+ to disable it. Multiple channels can

be used in parallel for higher LED current by tying their

LED1-8 pins together.

perForMAnce sUMMArY

The LT3760 data sheet gives a complete description of

the part, operation and applications information. The data

sheet must be read in conjunction with this demo manual

for demonstration circuit 1573A. The LT3760 is assembled

in a small 28-lead FE (4.4mm TSSOP) package with a

thermally enhanced ground pad. Proper board layout is

essential for maximum thermal performance. See the

Layout Considerations section in the data sheet.

Design files for this circuit board are available at

http://www.linear.com/demo

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.

(TA= 25°C)

PARAMETER CONDITION VALUE (TYPICAL)

PVIN Power Input Voltage Range Operating 20V to 28V

VIN Pin Input Voltage Range Operating 8V to 14V

Switching Frequency RT= 39.2k 1MHz

LED String Current ILED(1-8) R14 = 5.76k 100mA

OVP Open LED Voltage R8 = 11k, R7 = 20k 55V

Efficiency PVIN = 24V, VIN = 10V, VLED = 45V, ILED1-8 = 100mA 92%

Undervoltage Lockout R1 = 499k, R4 = 40.2k 20.1V

Low Voltage Turn-On (UVLO + VHYST) R1 = 499k, R4 = 40.2k 21.4V

Peak Switch Current Limit RS1 = 0.015Ω 3.3A

dc1573af

DEMO MANUAL DC1573A

qUick stArt proceDUre

Figure 1. Proper Measurement Setup Drawing

Demonstration circuit 1573A is easy to set up to evaluate

the performance of the LT3760. Follow theprocedure below:

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

used, tie PWM high or connect to REF on the PCB using

resistor R9.

1. Connect strings of LEDs with forward voltage less than

45V, but greater than the PVIN voltage, to the LED+ and

LED1-8 terminals on the PCB as shown in Figure 1. Tie

any unused LED1-8 pins directly to VOUT (LED+) before

power-up to disable that channel.

2. Connect the SHDN terminal to GND.

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

PVIN and GND terminals within the range specified on

the PCB. Make sure that the PVIN DC input voltage does

not exceed the forward voltage of the LED string.

4. With power off, connect the VIN power supply to the

VIN and GND terminals within the range specified on

the PCB.

5. Connect the PWM terminal. If PWM is not used, tie PWM

high or connect to REF on the PCB using resistor R9.

PWM must be pulled high to work.

6. Turn the PVIN power supply on.

7. Turn the VIN power supply on after PVIN.

8. Release the SHDN-to-GND connection.

9. Observe the LED strings running at the programmed

LED current.

Note:For PWM dimming, connecta PWM (100Hzor higher)

signal to the PWM terminal and observe the reduction of

brightness in the LED string when PWM dimming.

dc1573af

DEMO MANUAL DC1573A

terMinAl options

FAULT:The FAULT terminal is tied directly to the FAULT

pin. If there is a fault condition, the FAULT terminal is

pulled low. When there is no fault, the terminal is pulled

up to VIN. This terminal can be monitored with a voltage

meter, tied to the input of another device, or left floating.

SHDN/UVLO: This terminal is tied directly to the SHDN/

UVLO pin. A resistor divider from PVIN to GND sets the

voltage on this terminal/pin. These resistors can be easily

adjusted for both the UVLO level and the amount of rising

hysteresis. See the data sheet for details. The terminal can

also be used to shut the IC down and turn off the LEDs.

Tie the terminal directly to GND in order to place the IC

in shutdown and turn off the LEDs.

CTRL: This terminal is tied directly to the CTRL pin. As

assembled, there is a 1M resistor pulling the CTRL pin up

to REF. The CTRL pin voltage can be adjusted for analog

dimming as shown in the data sheet. Either a voltage on

the CTRL terminal can be driven to dim the LEDs or a

resistor divider (R2 and R5) from PVIN to GND can be

added to reduce the CTRL voltage as PVIN drops too low.

Pulling the CTRL pin to GND turns the LEDs off.

PWM: This terminal is tied directly to the PWM pin. As

shown in the data sheet, an input PWM waveform turns the

LEDs ON and OFF. Dimming frequency and dimming range

are discussed in the data sheet. When PWM dimming is

not being used, tie PWM to REF with a 0Ω resistor (R9)

or place a 3.3V or 5V DC source on the PWM terminal.

SYNC: This terminal is tied directly to the SYNC pin. As

assembled, SYNC is disabled and tied directly to GND

with a 0Ω resistor (R6). For SYNC to be used, R6 must

be removed and a SYNC signal must be applied to this

terminal.

INTVCC:This terminal is tied directly to the INTVCC pin.

This terminal is provided to be able to monitor the voltage

on the INTVCC regulator or to provide an external INTVCC

source to the IC. In some low voltage applications, INTVCC

can be tied directly to PVIN or VIN. See the data sheet for

details. For normal operation, leave this terminal floating.

LED+ and LED1-8: The eight LED+ terminals are the output

voltage of the boost regulator and they are all tied together

on the PCB. The anodes of the LED strings should be tied

to these terminals and the cathodes to LED1-8 terminals.

If an LED1-8 terminal is not used, it should be tied directly

to LED+. If all LED+ to LED1-8 connections are left float-

ing or are opened during operation, DC1573A powers the

output to 55V as programmed by OVPSET. It is okay to

connect LEDs to the LED+ and LED1-8 terminals when it

is powered to OVP. See data sheet for details.

LED1-8 terminals can be tied together to get more than

100mA per LED string. Pairs of LED1-8 terminals can be

tied together for 4× 200mA LED strings as an example.

Individually, each LED1-8 pin can source a maximum of

100mA, but they can be tied together for more.

dc1573af

DEMO MANUAL DC1573A

pArts list

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 1 CIN1 Capacitor, 1210 4.7µF 20% 25V X7R TDK C3225X7R1E475M

2 1 CIN2 Capacitor, 1210 4.7µF 10% 50V X7R AVX 12105C475KAT2A

3 5 C1, C2, C3, C4, C5 Capacitor, 1210 2.2µF 10% 100V X7R Murata GRM32ER72A225KA35L

4 1 C6 Capacitor, 0805 4.7µF 10% 10V X5R Taiyo Yuden LMK212BJ475KG-T

5 1 C7 Capacitor, 0402 2200pF 5% 50V X7R AVX 04025C222JAT2A

6 1 D1 Diode, Schottky Diodes Inc. PDS560

7 1 L1 Inductor, 10µH Sumida CDRH8D38NP-100NC

8 1 M1 MOSFET N-channel 60V Vishay Si7850DP-T1-E3

9 1 RS1 Resistor, 2010 0.015Ω 1% 1W IRC LRF2010LF-01-R015-F

10 1 RT Resistor, 0402 39.2kΩ 1% 1/16W Panasonic ERJ-2RKF3922X

11 1 R1 Resistor, 0603 499kΩ 1% 1/10W NIC NRC06F4993TRF

12 1 R4 Resistor, 0603 40.2kΩ 1% 1/10W NIC NRC06F4022TRF

13 2 R7, R10 Resistor, 0402 20kΩ 1% 1/16W NIC NRC04F2002TRF

14 1 R8 Resistor, 0402 11kΩ 1% 1/16W NIC NRC04F1102TRF

15 1 R11 Resistor, 0402 30.9kΩ 1% 1/16W NIC NRC04F3092TRF

16 1 R13 Resistor, 0402 10kΩ 5% 1/16W NIC NRC04J103TRF

17 1 R14 Resistor, 0402 5.76kΩ 1% 1/16W NIC NRC04F5761TRF

18 1 R18 Resistor, 0603 1MΩ 5% 1/10W Vishay CRCW06031M00JNEA

19 1 U1 IC, 8-Channel LED Driver Linear Technology LT3760EFE

Optional Electrical Components

1 0 C10 Do Not Stuff Option

2 0 R2, R3, R5, R16 Resistor, 0603 Option Option

3 1 R6 Resistor 0603 0Ω Jumper NIC NR06Z0TRF

4 0 R9, R12 Do Not Stuff Option

5 1 R15 Resistor, 0603 100kΩ 5% 1/10W NIC NRC06J104TRF

6 1 R17 Resistor, 0402 0Ω Jumper Vishay CRCW04020000Z0ED

Hardware

1 14 E1-E6, E13, E40-E46 Turret MILL MAX 2501-2-00-80-00-00-07-0

2 16 E7, E9-E11, E14-E16, E18-E20,

E22, E23, E27, E31, E35, E39

Turret MILL MAX 2308-2-00-80-00-00-07-0

dc1573af

DEMO MANUAL DC1573A

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

R13

10k

R13

10k

100mA

DC1573A F02

FAULT

SHDN/UVLO

CTRL

PWM

SYNC

OVPSET

REF

TSET

INTVCC

GATE

SENSE

VOUT

LED1

LED2

LED3

LED4

LED5

LED6

LED7

LED8

GND

LED1

LED2

LED3

LED4

LED5

LED6

LED7

LED8

E11

E14

E16

E18

E20

E22

ISET

PGND

VIN

R12

OPT

499k

OPT

R18

40.2k

R16

OPT

R10

20k

11k

20k

R11

30.9k

OPT

R15

100k

CIN1

4.7µF

25V

CIN2

4.7µF

25V

REF

4.7µF

10V

C10

OPT

8 7 6 5

123

RS1

0.015Ω

R17

0Ω

Si7850DP

PDS560

10µH

CDRH8D38NP C1

2.2µF

100V

1210

2.2µF

100V

1210

2.2µF

100V

1210

2.2µF

100V

1210

2.2µF

100V

1210

LED+

E10

E15

E19

E23

E27

E31

E35

E39

E42

E44

GND

2200pF

39.2k

1MHz

LT3760EFE

E45

GND

10V TO 14V

GND

FAULT

SHDN/UVLO

PVIN

20V TO 28V

E41

GND E40

CTRL E5

PWM E6

SYNC E13

GND

INTVCC

E43

E46

dc1573af

DEMO MANUAL DC1573A

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

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

 LINEAR TECHNOLOGY CORPORATION 2011

LT 0311 • 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

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