Linear Technology DC1160 Guía de configuración rápida
1
dc1160f
DEMO MANUAL DC1160
DESCRIPTION
LT3518: Full-Featured
LED Driver with 2.3A
Switch Current
Demonstration circuit 1160 is a full-featured LED driver
with 2.3A switch current featuring the LT
®
3518. The board
is optimized to drive a 330mA LED string with a total LED
voltage between the input voltage and 40V in a boost to-
pology. The high input voltage range, high efficiency low
side internal 2.3A NPN power switch, low voltage floating
current sense amplifier, soft-start, high side PMOS PWM
gate driver, high PWM dimming ratio, overvoltage protec-
tion, shutdown control pin, analog LED current dimming
control,andexternallyprogrammableswitchingfrequency
(with sync) make the LT3518 an extremely versatile and
powerful LED driving IC.
The LT3518 has a 45V switch with 2.3A peak switch cur-
rent limit rating. DC1160 has overvoltage protection at
40V if the LEDs are open or not properly attached to the
terminals on the PCB. The shutdown function is activated
by pulling the shutdown terminal to ground. In shutdown
the boost configuration allows the input voltage to be seen
on the output and if the attached LED array leaks current
at the input voltage, the LEDs may not completely turn off.
If the top gate is installed, it will provide shutdown output
disconnect and the LEDs will turn off during shutdown.
The CTRL terminal can be used to analog dim the LED
current. In order to use the CTRL terminal, R6 (0Ω) pull-
up short resistor must be removed and replaced with a
resistor divider from VREF to GND or an external voltage
on the CTRL terminal.
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.
The high side PMOS PWM dimming MOSFET can be
used to achieve 3000:1 PWM dimming ratio. The board
is programmed for 1MHz oscillator frequency, but can
be adjusted by changing R14. Higher frequency results
in higher PWM dimming ratio.
The VIN pin can be tied directly to PVIN for simplicity or
powered from an additional low voltage input such as
3.3V for higher efficiency operation and lower on-chip
power dissipation.
A few simple modifications can be made to DC1160 in
order to convert the board from a boost LED driver to a
buck mode or buck-boost mode LED driver. Please consult
the data sheet for schematic details and the factory for
customization details.
The LT3518 data sheet gives a complete description of the
part, operation andapplicationsinformation. The datasheet
must be read in conjunction with this Quick Start Guide for
demonstration circuit 1160. The LT3518 is assembled in a
small 16-lead plastic (4mm ×4mm) QFN UF package with
a thermally enhanced ground pad. Proper board layout is
essential for maximum thermal performance. See the data
sheet section Layout Considerations.
Design files for this circuit board are available at
http://www.linear.com/demo
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dc1160f
DEMO MANUAL DC1160
QUICK START PROCEDURE
DC1160 is easy to set up to evaluate the performance of
the LT3518. Follow the procedure below:
Note:Makesurethat the PVIN inputvoltagedoesnotexceed
40V and that the VIN input voltage does not exceed 30V.
1. Connect a string of LEDs with forward voltage less than
40V, but greater than the PVIN input voltage, to the LED+
and GND terminals on the PCB as shown.
2. With power off, connect a 3.3V input power supply to
the VIN and GND terminals on the PCB.
3. With power off, connect a 3V to 40V input power supply
to PVIN and GND terminals on the PCB. PVIN should
not exceed the attached LED string voltage.
4. Connect a 3.3V source to PWM and GND.
5. Turn PVIN power on.
6. Turn VIN power on and observe the regulated LED cur-
rent, the circuit efficiency, etc. without looking directly
at the LEDs.
7. For PWM dimming, tie a 100Hz,3V to 5V PWM waveform
to the PWM terminal and GND and observe the PWM
dimming LED current and PWM gate waveforms.
8. For shutdown, tie the SHDN terminal to GND and
observe the LED current dropping to zero and the VIN
input current dropping to about 65mA with R4 installed
(VIN/51k).
PWM DUTY CYCLE (%)
0
EFFICIENCY (%)
60
80
100
80
DC1160 F01
40
50
70
90
30
20 20 40 60 100
VIN = 12V
CTRL = VREF
Figure 1. DC1160A Efficiency 30V LED String, PVIN = VIN = 12V
PWM
5V/DIV
ILED
200mA/DIV
IL1
1A/DIV
1μs/DIV DC1160 F02
Figure 2. 3000:1 PWM Dimming at 100Hz,
PVIN = 12V, VLED = 30V
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4
dc1160f
DEMO MANUAL DC1160
PARTS LIST
ITEM QUANTITY REFERENCE PART DESCRIPTION MANUFACTURER, PART NUMBER
REQUIRED CIRCUIT COMPONENTS:
1 1 C5 Capacitor, X7R, 4.7nF, 25V, 20% 0402 AVX, 04023C472MAT2A
2 2 C3,C4 Capacitor, X7R, 0.01μF, 16V, 10% 0402 AVX, 0402YC103KAT
31 C
VIN Capacitor, X7R, 1μF, 50V, 10% 1206 Murata, GRM31MR71H105KA88L
42C
PVIN, COUT Capacitor, X5R, 2.2μF, 50V, 10% 1206 Murata, GRM31CR71H225KA88L
5 1 D1 Schottky Rectifier, 2.1A\60V, SMA Vishay, 10MQ060NPBF
6 1 L1 Inductor, 10μH Sumida, CDRH8D28-100NC
7 1 R1 Resistor, Chip, 0.300Ω, 1/4W, 1% 1206 Vishay, CRCW1206R300FNTA
8 1 R8 Resistor, Chip, 392k, 1/16W, 1% 0402 Vishay, CRCW0402392KFKED
9 1 R12 Resistor, Chip, 10k, 1/16W, 1% 0402 Vishay, CRCW040210K0FKED
10 1 R13 Resistor, Chip, 5.1k, 1/16W, 1% 0402 Vishay, CRCW04025K10FKEA
11 1 R14 Resistor, Chip, 16.5k, 1/16W, 1% 0402 Vishay, CRCW040216K5FKEA
12 1 U1 I.C., LT3518EUF Linear Tech., LT3518EUF#PBF
ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS:
1 0 C1,C2,C6 OPT
2 1 Q1 MOSFET, P-Channel 40-V (D-S) SOT23 Vishay, Si2319DS-T1-E3
3 2 R6, R7 Resistor, Chip, 0, 0402 Vishay, CRCW04020000Z0ED
4 1 R4 Resistor, Chip, 51k, 1/16W, 5% 0402 AAC, CR05-513JM
5 0 R2, R3, R5,
R9-R11, R15, R16
OPT
HARDWARE FOR DEMO BOARD ONLY:
1 12 E1 to E12 Testpoint, Turret, 0.094" Mill-Max, 2501-2
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dc1160f
DEMO MANUAL DC1160
SCHEMATIC DIAGRAM
A
A
B
B
C
C
D
D
E
E
4 4
3 3
22
1 1
1206
Linear Technology Has Made A Best Effort To Design A
CIN Boost
1206
CircuitT
hat Meets Customer-Supplied Specifications;
However,ItRemains The Customer's Responsibility To
40V Transients
VerifyProper And ReliableOperation In The Actual
Application. Component Substitution And Printed
Circuit Board LayoutMay Significantly Affect Circuit
Performance Or Reliability. Contact Linear Technology
Applications Engineering For Assistance.
ThisCircui
tI
sProprietaryToLin
ear Technology And
Supplied ForUse With Linear Technology Parts.
Customer Notice
LTCCONFIDENTIAL - FOR CUSTOMER USEONL
Y
Demo Circuit 1160A LT3518EUF
Full-Featured LED Driver with 2.3A Switch Current
LINEAR TECHNOLOGY CORPORATION
1630McCAR
THY BLVD.
MILPITAS, CA. 95035
PHONE (408) 432-1900 FAX (408) 434-0507
A
11
Wednesday,J
uly 18, 2007
Title
Size Document Number Rev
Date: Sheet of
PVIN
OUT
VIN
LED+
LED+
OUT
OUT
PVIN
OUT
PVIN
R5
Opt.
E2
LED+
330mA
Q1
Si2319DS
2
1
3
R16
Opt.
D1
10MQ060N
2 1
E10
GND
R8
392k
R1
0.300
1%
1206
CVIN
1uF
50V
E7
CTRL
E5
GND
E9
SYNC
R4
51k
E1
OUT
R7
0
E4
PVIN
3V-40V
+
Opt.
C1
C6
2.2uF
Opt.
C5
4.7nF
R6
0
COUT
2.2uF
50V
E12
GND
R2
Opt.
R10
Opt.
E8
PWM
E3
VIN
3V-30V
E11
GND
R12
10k
R14
16.5k
1%
1MHz
CPVIN
2.2uF
50V
+
Opt.
C2
R9
Opt.
C3
0.01uF
R3
Opt.
U1
LT3518EUF
3
4
2
7
1
5
6
8
9
10
11
12
13
14
15
16
17
VIN
SHDN
SW
SYNC
SW
VREF
RT
SS
PWM
CTRL
VC
FB
TGEN
ISN
ISP
TG
GND
R13
5.1k
Q2
Opt.
1
23
E6
SHDN
L1
10uH
R15
Opt.
C4
0.01uF
R11
Opt.
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