Linear Technology DC1576 Quick setup guide

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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

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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.

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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.

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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

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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 NC PWM SYNC OVPSET REF TSET INTVCC
16 15
1 5
27 17 28
3 2
13
GATE
SENSE
VOUT
LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8
GND
12 11 18 6 7 8 9 20 21 22 23 24
LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8
E7 E9
E11 E14 E16 E18 E20 E22
VC
ISET
PGND
PGND
PGND
RT
26
4
10
19
29
25
VIN
R12 OPT
R2 OPT
R3 OPT
R1 499k 1%
R9 OPT
R6 OPT
R18 1M
R4 40.2k 1%
R16 OPT
R10 20k 1% R8 11k 1%
R7 20k 1%
R11 30.9k 1%
R5 OPT
R15 100k
CIN1 4.7µF 25V
CIN2
4.7µF 25V
REF
C6 4.7µF 10V
C10 OPT
14
4
8 7 6 5
123
RS1 0.015Ω
R17
0Ω
M1 Si7850DP
D1
PDS560
L1
10µH
CDRH8D38NP C1
2.2µF 100V 1210
C2 2.2µF 100V 1210
C3 2.2µF 100V 1210
C4 2.2µF 100V 1210
C5 2.2µF 100V 1210
LED+ LED+ LED+ LED+ LED+ LED+ LED+ LED+
E10 E15 E19 E23 E27 E31 E35 E39 E42 E44
GND GND
C7 2200pF
RT 39.2k 1MHz
U1
LT3760EFE
E45 E2 E1 E3
GND
V
IN
10V TO 14V
GND
FAULT
SHDN/UVLO
PVIN
20V TO 28V
E41
GND E40
CTRL E5
PWM E6
SYNC E13
E4
GND
INTVCC
E43 E46

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DEMO MANUAL DC1573A
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2011
LT 0311 • PRINTED IN USA
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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
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