DEMO MANUAL DC1573A
LT3760
8-Channel 100mA
High Voltage LED Driver
Description
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 V
IN
terminal is
powered from 10V to 14V input separated from the 24V
PV
IN
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.
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.
perForMAnce sUMMArY
PARAMETER
PV
IN
Power Input Voltage Range
V
IN
Pin Input Voltage Range
Switching Frequency
LED String Current I
LED(1-8)
OVP Open LED Voltage
Efficiency
Undervoltage Lockout
Low Voltage Turn-On (UVLO + V
HYST
)
Peak Switch Current Limit
(T
A
= 25°C)
CONDITION
Operating
Operating
R
T
= 39.2k
R14 = 5.76k
R8 = 11k, R7 = 20k
PV
IN
= 24V, V
IN
= 10V, V
LED
= 45V, I
LED1-8
= 100mA
R1 = 499k, R4 = 40.2k
R1 = 499k, R4 = 40.2k
R
S1
= 0.015Ω
VALUE (TYPICAL)
20V to 28V
8V to 14V
1MHz
100mA
55V
92%
20.1V
21.4V
3.3A
dc1573af
1
DEMO MANUAL DC1573A
qUick stArt proceDUre
Demonstration circuit 1573A is easy to set up to evaluate
the performance of the LT3760. Follow the procedure 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 PV
IN
voltage, to the LED+ and
LED1-8 terminals on the PCB as shown in Figure 1. Tie
any unused LED1-8 pins directly to V
OUT
(LED+) before
power-up to disable that channel.
2. Connect the
SHDN
terminal to GND.
3. With power off, connect the PV
IN
power supply to the
PV
IN
and GND terminals within the range specified on
the PCB. Make sure that the PV
IN
DC input voltage does
not exceed the forward voltage of the LED string.
4. With power off, connect the V
IN
power supply to the
V
IN
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 PV
IN
power supply on.
7. Turn the V
IN
power supply on after PV
IN
.
8. Release the
SHDN-to-GND
connection.
9. Observe the LED strings running at the programmed
LED current.
Note:
For PWM dimming, connect a PWM (100Hz or higher)
signal to the PWM terminal and observe the reduction of
brightness in the LED string when PWM dimming.
Figure 1. Proper Measurement Setup Drawing
dc1573af
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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 V
IN
. 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 PV
IN
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 PV
IN
to GND can be
added to reduce the CTRL voltage as PV
IN
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.
INTV
CC
:
This terminal is tied directly to the INTV
CC
pin.
This terminal is provided to be able to monitor the voltage
on the INTV
CC
regulator or to provide an external INTV
CC
source to the IC. In some low voltage applications, INTV
CC
can be tied directly to PV
IN
or V
IN
. 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
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DEMO MANUAL DC1573A
pArts list
ITEM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
1
2
3
4
5
6
Hardware
1
2
14
16
E1-E6, E13, E40-E46
E7, E9-E11, E14-E16, E18-E20,
E22, E23, E27, E31, E35, E39
Turret
Turret
MILL MAX 2501-2-00-80-00-00-07-0
MILL MAX 2308-2-00-80-00-00-07-0
QTY
1
1
5
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
0
0
1
0
1
1
REFERENCE
CIN1
CIN2
C1, C2, C3, C4, C5
C6
C7
D1
L1
M1
RS1
RT
R1
R4
R7, R10
R8
R11
R13
R14
R18
U1
C10
R2, R3, R5, R16
R6
R9, R12
R15
R17
PART DESCRIPTION
Capacitor, 1210 4.7µF 20% 25V X7R
Capacitor, 1210 4.7µF 10% 50V X7R
Capacitor, 1210 2.2µF 10% 100V X7R
Capacitor, 0805 4.7µF 10% 10V X5R
Capacitor, 0402 2200pF 5% 50V X7R
Diode, Schottky
Inductor, 10µH
MOSFET N-channel 60V
Resistor, 2010 0.015Ω 1% 1W
Resistor, 0402 39.2kΩ 1% 1/16W
Resistor, 0603 499kΩ 1% 1/10W
Resistor, 0603 40.2kΩ 1% 1/10W
Resistor, 0402 20kΩ 1% 1/16W
Resistor, 0402 11kΩ 1% 1/16W
Resistor, 0402 30.9kΩ 1% 1/16W
Resistor, 0402 10kΩ 5% 1/16W
Resistor, 0402 5.76kΩ 1% 1/16W
Resistor, 0603 1MΩ 5% 1/10W
IC, 8-Channel LED Driver
Do Not Stuff
Resistor, 0603 Option
Resistor 0603 0Ω Jumper
Do Not Stuff
Resistor, 0603 100kΩ 5% 1/10W
Resistor, 0402 0Ω Jumper
MANUFACTURER/PART NUMBER
TDK C3225X7R1E475M
AVX 12105C475KAT2A
Murata GRM32ER72A225KA35L
Taiyo Yuden LMK212BJ475KG-T
AVX 04025C222JAT2A
Diodes Inc. PDS560
Sumida CDRH8D38NP-100NC
Vishay Si7850DP-T1-E3
IRC LRF2010LF-01-R015-F
Panasonic ERJ-2RKF3922X
NIC NRC06F4993TRF
NIC NRC06F4022TRF
NIC NRC04F2002TRF
NIC NRC04F1102TRF
NIC NRC04F3092TRF
NIC NRC04J103TRF
NIC NRC04F5761TRF
Vishay CRCW06031M00JNEA
Linear Technology LT3760EFE
Option
Option
NIC NR06Z0TRF
Option
NIC NRC06J104TRF
Vishay CRCW04020000Z0ED
Required Circuit Components
Optional Electrical Components
dc1573af
4
V
IN
10V TO 14V
R16
OPT
8 7 6 5
14
16
FAULT
GATE
R17
0
1 2 3
R
S1
0.015Ω
E7
E9
E11
E14
E16
E18
E20
E22
E10
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
LED+
LED+
LED+
LED+
LED+
LED+
LED+
LED+
E15
E19
E23
E27
E31
E35
E39
SHDN/UVLO
CTRL
NC
V
OUT
PWM
SYNC
OVPSET
LED4
3
REF
LED6
LED7
LED8
GND
24
23
22
21
LED5
20
9
LED3
8
LED2
7
LED1
6
18
U1
LT3760EFE
C10
OPT
SENSE
11
M1
Si7850DP
15
1
R5
OPT
5
27
17
28
R9
OPT
R7
20k
1%
R10
20k
1%
R11
30.9k
1%
C6
4.7µF
10V
VC
ISET
PGND
PGND
PGND
RT
DC1573A F02
E45
C
IN1
4.7µF
25V
R12
OPT
L1
10µH
CDRH8D38NP
D1
PDS560
GND
E2
R15
100k
PV
IN
20V TO 28V
R1
499k
1%
R2
OPT
V
IN
12
4
C
IN2
4.7µF
25V
C1
2.2µF
100V
1210
C2
2.2µF
100V
1210
C3
2.2µF
100V
1210
C4
2.2µF
100V
1210
E1
scheMAtic DiAgrAM
GND
E41
R3
OPT
C5
2.2µF
100V
1210
FAULT
E3
SHDN/UVLO
R4
40.2k
1%
E4
GND
E40
CTRL
E5
PWM
E6
SYNC
E13
GND
E43
R18
1M
R6
OPT
R8
11k
1%
REF
2
TSET
13
INTV
CC
E42
E44
GND
GND
E46
26
4
10
19
29
25
RT
39.2k
1MHz
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.
R13
10k
C7
2200pF
R13
10k
100mA
INTV
CC
DEMO MANUAL DC1573A
dc1573af
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