DC1706A - Demo Manual

DEMO MANUAL DC1706A
LT3796
100V LED Controller with
Current Monitor
DESCRIPTION
DC1706A is a 100V LED controller with an input current
monitor. It is a single switch boost LED driver with LED+
to GND short circuit protection. It accepts an input voltage from 8V to 100V (7.5V UVLO and 8.7V turn-on), and
drives up to 85V of LEDs at 400mA (when PVIN is less than
VLED). DC1706A features both PWM and analog dimming
of the LED string. It has a VMODE flag that indicates when
the LED string has been removed and it has a FAULT flag
that indicates that the output has been shorted to GND. In
both cases, the IC remains in control and well protected.
DC1706A features high efficiency at 300kHz switching
frequency. At high LED string voltages up to 85V and
400mA of LED current, the single switch controller has
93% efficiency. There are input current (CSOUT) and output current (ISMON) monitor pins that deliver a voltage
proportional to the current for quick diagnostics.
Small ceramic input and output capacitors are used to save
space and cost. The open LED overvoltage protection uses
the IC’s constant voltage regulation loop to regulate the
output to approximately 92.5V if the LED string is opened
although it may reach 96.5V peak during transient from
running LEDs to open.
For low input voltage operation, the CTRL pin voltage is
reduced as the input voltage drops below 9V, reducing
LED brightness and restraining the peak switch currents
in order to limit inductor and switch size. UVLO turns the
LEDs off when VIN drops below 7.5V.
DC1706A PWM dimming is simple. The topside PWM
dimming MOSFET (M2) turns the LED string on and off
with an input to the PWM dimming terminal. For the highest PWM dimming ratio, it is recommended to use 100Hz
as a PWM dimming frequency. Information regarding
PWM dimming ratios and performance can be found in
the LT3796 data sheet in the applications section. Analog
dimming is also simple to use with a single voltage source
on the CTRL terminal.
Modifications can be made to DC1706A in order to convert
the board to higher or lower power or from an LED driver
to a constant voltage regulator or battery charger. It can
easily be changed from a boost topology to a SEPIC, buck
mode, or buck-boost mode LED driver. Please consult the
factory or refer to the LT3796 data sheet for details.
The LT3796 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 DC1706A. The LT3796 is assembled in a 28lead plastic TSSOP FE 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
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.
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DEMO MANUAL DC1706A
PERFORMANCE SUMMARY
(TA = 25°C)
PARAMETER
CONDITIONS
UNITS
Input Voltage PVIN Range
Operating
7.5V to VLED
Switching Frequency
R18 = 26.1k
300kHz
ILED
RS2 = 0.62Ω, 9V < PVIN < VLED
400mA
Low PVIN ILED (CTRL Foldback)
RS2 = 0.62Ω, PVIN = 8V
350mA
VLED Range
R5 = 1M, R9 = 13.7k
PVIN < VLED < 85V
Open LED Voltage
R5 = 1M, R9 = 13.7k
92.5V
Typical Efficiency
PVIN = 14V, VLED = 85V, ILED = 400mA
93%
Under Voltage Lockout (Falling Turn-Off)
R1 = 499k and R8 = 100k
7.5V
Under Voltage Lockout (Rising Turn-On)
R1 = 499k and R8 = 100k
8.7V
VINTVCC
Operating
7.7V
Peak Switch Current Limit
RS3 = 0.015Ω
6.6A
Suggested Maximum PWM Dimming Ratio
fPWM = 100Hz, PVIN=12V, VLED = 85V, ILED = 400mA
100:1
QUICK START PROCEDURE
DC1706A is easy to set up to evaluate the performance of
the LT3796. Follow the procedure below:
5. Turn the input power supply on and make sure the
voltage is between 8V and VLED.
NOTE: PWM must be pulled high to run. If PWM is not
used, connect PWM to a 3.3V or 5V source or to VREF on
the PCB using 0Ω resistor R24.
6. Release the EN/UVLO-to-GND connection.
1. Connect a string of LEDs that will run with forward voltage less than 85V, but greater than PVIN, to the LED+
and GND terminals on the PCB as shown in Figure 1.
8. Observe the CSOUT and ISMON input and output current monitor voltages.
2. Connect the EN/UVLO terminal to GND.
3. With power off, connect the input power supply to the
PVIN and GND terminals. Make sure that the PVIN DC
input voltage will not exceed 100V (or VLED).
4. Connect the PWM terminal. If PWM is not used, connect
PWM to a 3.3V or 5V source or to VREF on the PCB using 0Ω resistor R24. PWM must be pulled high to run.
7. Observe the LED string running at the programmed
LED current.
9. For PWM dimming, connect a PWM (100Hz or higher is
recommended) signal to the PWM terminal. For analog
dimming, connect a DC voltage between 0V and 2V to
the CTRL terminal.
10. Observe the reduction of brightness in the LED string
when PWM or analog dimming.
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DEMO MANUAL DC1706A
QUICK START PROCEDURE
Figure 1. Test Procedure Setup Drawing for DC1706A
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3
DEMO MANUAL DC1706A
QUICK START PROCEDURE
100
85VLED 400mA
98
96
94
EFFICIENCY (%)
92
90
88
86
84
82
80
0
10
20
30
50
40
PVIN INPUT VOLTAGE (V)
60
70
80
90
DC1706a F02
Figure 2. DC1706A Efficiency with 85V LEDs at 400mA
ILED
100mA/DIV
100:1
1000:1
85VLED
PVIN = 12V
500:1
250:1
125:1
fPWM = 100Hz
DC1706a F03
Figure 3. DC1706A 100Hz 100:1 to 1000:1 PWM Dimming Waveforms at 12V PVIN and 85V VLED
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DEMO MANUAL DC1706A
QUICK START PROCEDURE
0.45
0.40
0.35
ILED (A)
0.30
TURN-ON
(RISING)
0.25
UNDER
VOLTAGE
LOCKOUT
(FALLING)
0.20
0.15
0.10
0.05
0
7
7.5
8
8.5
9
9.5
PVIN (V)
10
10.5
11
11.5
12
DC1706a F04
Figure 4. DC1706A CTRL LED Current Foldback at Low PVIN with UVLO Falling and Rising
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DEMO MANUAL DC1706A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
2
C1, C2
CAP, X7S 4.7μF 100V 10% 1210
TDK C3225X7S2A475K
2
5
C3, C4, C5, C6, C12
CAP, X7R 2.2μF 100V 10% 1210
MURATA GRM32ER72A225KA35L
3
1
C8
CAP, X5R 4.7μF 10V 10% 0603
AVX 0603ZD475KAT2A
4
1
C9
CAP, X7R 0.01μF 25V 10% 0603
AVX 06033C103KAT2A
5
1
C11
CAP, X7R 0.1μF 25V 10% 0603
AVX 06033C104KAT2A
6
1
D1
SCHOTTKY DIODE 100V 5A POWERDI5
DIODES INC PDS5100H
7
1
L1
INDUCTOR, 22μH HC9-SERIES
COOPER BUSSMANN HC9-220-R
8
1
M1
MOSFET N-CHAN, 100V/15A LFPAK
RENESAS RJK1051DPB-00-J5 #PbF
9
1
M2
MOSFET P-CHAN, 100V POWERPAK 1212-8
SILICONIX Si7113DN-T1-E3 #PbF
10
1
RS2
RES, LRC 0.620 0.5W 1% 2010
IRC LR2010LF-01-R620-F
11
1
RS3
RES, 0.015 0.5W 1% 2010
VISHAY WSL2010R0150FEA
12
1
R5
RES, CHIP 1M 0.06W 1% 0402
VISHAY CRCW04021M00FKED
13
1
R9
RES, CHIP 13.7k 0.06W 1% 0402
VISHAY CRCW040213K7FKED
14
1
R16
RES, CHIP 4.7k 0.06W 5% 0402
VISHAY CRCW04024K70JNED
15
1
R18
RES, CHIP 26.1k 0.06W 1% 0402
VISHAY CRCW040226K1FKED
16
1
U1
100V LED CONTROLLER IC TSSOP28-FE/EB
LINEAR TECHNOLOGY LT3796
Optional Electrical Components
1
0
C13, C14, C15
CAP, 1210 OPTIONAL
2
1
C16
CAP, X7R 0.01μF 25V 10% 0603
AVX 06033C103KAT2A
3
1
C17
CAP, X7R 0.1μF 25V 10% 0603
AVX 06033C104KAT2A
4
1
D2
SCHOTTKY RECT, 150V/1A SMA
FAIRCHILD SEMI ES1C
5
0
D3
DIODE, SOD-123 OPTIONAL
6
0
M3
MOSFET SOT23 OPTIONAL
7
1
Q1
TRANS, PNP SOT23
ZETEX/DIODES INC FMMT589
8
1
RS1
RES, 0.025 0.5W 1% 2010
VISHAY WSL2010R0250FEA
9
1
R1
RES, CHIP 499k 0.06W 1% 0402
VISHAY CRCW0402499KFKED
10
3
R2, R4, R17
RES/JUMPER, CHIP 0Ω 1/16W 1A 0402
VISHAY CRCW04020000Z0ED
11
1
R3
RES, CHIP 2k 0.06W 1% 0402
VISHAY CRCW04022K00FKED
12
1
R6
RES/JUMPER, CHIP 0Ω 1/4W 1A 1206
VISHAY CRCW12060000ZOEA
13
1
R7
RES, CHIP 1M 0.06W 1% 0402
VISHAY CRCW04021M00FKED
14
1
R8
RES, CHIP 100k 0.06W 1% 0402
VISHAY CRCW0402100KFKED
15
1
R10
RES, CHIP 137k 0.06W 1% 0402
VISHAY CRCW0402137KFKED
16
0
R11, R12, R15, R19 TO R22,
R25, R27, R28, R31, R33
RES 0402 OPTIONAL
17
2
R13, R14
RES, CHIP 100k 0.06W 5% 0402
18
0
R24, R30, R32
RES, 0603 OPTIONAL
19
1
R26
RES/JUMPER, Chip 0Ω 1/16W 1A 0603
VISHAY CRCW06030000Z0EA
20
1
R29
RES, CHIP 82.5k 0.06W 1% 0402
VISHAY CRCW040282K5FKED
21
0
R34
RES, 1206 OPTIONAL
VISHAY CRCW0402100KJNED
Optional Hardware
1
18
E1 TO E18
TURRET, TESTPOINT
MILL MAX 2501-2-00-80-00-00-07-0
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DEMO MANUAL DC1706A
SCHEMATIC DIAGRAM
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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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
7
DEMO MANUAL DC1706A
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
Copyright © 2004, Linear Technology Corporation
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Linear Technology Corporation
LT 0512 • PRINTED IN USA
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●
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