DC2079A - Demo Manual

DEMO MANUAL DC2079A
LT3954
40VIN 40VOUT LED Driver
Description
Demonstration circuit 2079A is a 40VIN, 40VOUT LED driver.
It generates its own PWMOUT waveform from its internal
PWM generator for accurate PWM dimming with up to
33:1 brightness ratio. It accepts an input voltage from
5V to 30V and drives up to 32V of LEDs at 650mA (when
PVIN is less than VLED). DC2079A features both PWM and
analog dimming of the LED string. It has an OPENLED flag
that indicates when the LED string has been removed.
by the capacitance on the PWM pin (C16 gives 300Hz for
DC2079A). The PWMOUT duty cycle is determined by the
voltage on the DIM terminal. Between 0V and 8V VDIM
gives between 3% and 97% PWM duty cycle. Information
regarding PWM dimming ratios and performance can be
found in the LT3954 data sheet in the applications section. Analog dimming is also simple to use with a single
voltage source on the CTRL terminal.
DC2079A features high efficiency at 350kHz switching
frequency. At high LED string voltages up to 32V and
650mA of LED current, the single switch controller has
94.6% efficiency (14V input). The LT3954 has an internal
40V, 5.4A switch that simplifies the schematic and layout.
Modifications can be made to DC2079A in order to convert
the board to power different LED strings 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 the LT3954 data sheet for details.
It can be modified to provide LED+ to GND short-circuit
protection as well.
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 35V if the LED string is opened
although it may reach 38V peak during transient from
running LEDs to open string.
For low input voltage operation, the CTRL pin voltage is
reduced as the input voltage drops below 8.5V, 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 5.3V.
DC2079A PWM dimming is simplified when compared
with other LED drivers. The LT3954 generates its own
PWMOUT dimming waveform at a frequency determined
The LT3954 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 DC2079A. The LT3954EUHE
is assembled in a 36-lead plastic QFN package with two
thermal pads underneath the IC. 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, 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 DC2079A
Performance Summary
Specifications are at TA = 25°C
PARAMETER
CONDITION
VALUE (TYPICAL)
Input Voltage PVIN Range
Operating
5V to VLED (Up to 40V)
Switching Frequency
R1 = 28.7k
350kHz
ILED
RS1 = 0.39Ω 8.4V < PVIN < VLED (40V)
645mA
Low PVIN ILED (CTRL Foldback)
RS1 = 0.39Ω, PVIN = 6.0V
RS1 = 0.39Ω , PVIN = 7.0V
RS1 = 0.39Ω, PVIN = 8.0V
486mA
577mA
640mA
VLED Range
R7 = 1M, R8 = 37.4k
PVIN < VLED < 32V
Open LED Voltage
R7 = 1M, R8 = 37.4k
34.8V
Typical Efficiency
PVIN =14V, VLED = 32V, ILED = 645mA PWM = INTVCC
94.6%
PVIN Undervoltage Lockout (Falling Turn-Off)
R3 = 499k and R4 = 147k
5.3V
PVIN Undervoltage Lockout (Rising Turn-On)
R3 = 499k and R4 = 147k
6.5V
INTVCC
Operating
7.85V
Peak Switch Current Limit
5.4A
PWMOUT Dimming Duty Cycle
VDIM = 8.0V
VDIM = 4.0V
VDIM = 1.5V
VDIM = 0V
97.5%
50%
10%
3.1%
Internal PWM Dimming Frequency
C16 = 0.047µF, 0V < VDIM < 8V
300Hz
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2
DEMO MANUAL DC2079A
Quick Start Procedure
Demonstration circuit DC2079A is easy to set up to evaluate the performance of the LT3954. Follow the procedure
below:
5. Turn the input power supply on and make sure the
voltage is between 6.5V and 40V (or VLED) to start.
1. Connect a string of LEDs that will run with forward
voltage less than or equal to 32V, but greater than the
intended PVIN, to the LED+ and LED– terminals on the
PCB as shown in Figure 1.
7. Observe the LED string running at the pro-grammed
LED current and brightness related to the programmed
PWMOUT duty cycle.
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 40V (or VLED).
4. Connect the DIM terminal to a voltage between 0V and
8V to set the internal PWMOUT dimming duty cycle. If
this terminal is left floating the converter will run with
approximately 12% PWMOUT dimming duty cycle. Pull
the PWM terminal high to INTVCC to set the converter
at 100% duty cycle.
6. Release the EN/UVLO-to-GND connection.
8. To change the brightness with PWM dimming, simply
vary the VDIM voltage between 0V and 8V with the PWM
terminal floating.
9. To change the brightness with analog dimming, simply attach a voltage source on the CTRL terminal and
reduce the voltage below 1.2V.
10.Observe the reduction of brightness in the LED string
when PWM or analog dimming.
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DEMO MANUAL DC2079A
Quick Start Procedure
Figure 1. Test Procedure Setup Drawing for DC2079A
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4
DEMO MANUAL DC2079A
Quick Start Procedure
100
32VLED 650mA
PWM = INTVCC
98
EFFICIENCY (%)
96
94
92
90
88
86
84
82
80
5
15
10
20
30
25
PVIN (V)
DC2079A F02
Figure 2. DC2079A Efficiency with 32V LEDs at 650mA
and 100% PWMOUT Duty Cycle
VDIM = 8V
DCPWM = 97.5%
VDIM = 3.9V
DCPWM = 47%
ILED
500mA/DIV
VDIM = 1.5V
DCPWM = 10%
VDIM = 0V
DCPWM = 3.1%
DC2079A F03
VIN = 12V
VLED = 32V
Figure 3. DC2079A 300Hz PWM Dimming Waveforms
at Different PWMOUT Duty Cycles
0.7
0.6
ILED (A)
0.5
0.4
UNDER
VOLTAGE
LOCKOUT
0.2 (FALLING)
0.3
TURN-ON
(RISING)
0.1
0
4
5
6
7
8
PVIN (V)
9
10
11
12
DC2079A F04
Figure 4. DC2079A CTRL LED Current Foldback at
Low PVIN with UVLO (Falling and Rising)
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5
DEMO MANUAL DC2079A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Cap., X5R 1µF 50V 20% 1206
TDK C3216X5R1H105M
Required Circuit Components
1
1
C1
2
1
C2
Cap., X5R 10µF 50V 20% 1210
Taiyo Yuden UMK325BJ106MM-T
3
2
C4, C5
Cap., X5R 4.7µF 50V 20% 1210
Taiyo Yuden UMK325BJ475MM-T
4
1
C9
Cap., X7R 4.7nF 25V 20% 0603
AVX 06033C472MAT2A
5
1
C10
Cap., X7R 0.01µF 25V 10% 0603
AVX 06033C103KAT2A
6
1
C11
Cap., X7R 1µF 10V 10% 0603
Taiyo Yuden LMK107BJ105KA
7
1
C16
Cap., X7R 47nF 16V 20% 0603
Taiyo Yuden EMK107BJ473MA
8
1
D1
Schottky Diode 5A PowerDi5
Diodes Inc. PDS560-13
9
1
L1
Inductor, 22µH
Cooper Coiltronics DR125-220
10
1
M1
Mosfet N-Chan., 40V SOT23
Siliconix Si2318CDS-T1-GE3
11
1
RS1
Res., Chip 0.39, 0.25W 1% 1206
Panasonic ERJ-8RQFR39V
12
1
R1
Res., Chip 28.7k 0.06W 1% 0402
Vishay CRCW040228K7FKED
13
1
R2
Res., Chip 5.1k 0.06W 5% 0402
Vishay CRCW04025K10JNED
14
1
R7
Res., Chip 1.00M 0.06W 1% 0603
Vishay CRCW06031M00FKEA
15
1
R8
Res., Chip 37.4k 0.06W 1% 0402
Vishay CRCW040237K4FKED
16
1
R21
Res., Chip 124k 0.06W 1% 0603
Vishay CRCW0603124KFKEA
17
1
U1
I.C.,40Vin/ 40Vout LED Driver
Linear Tech. Corp. LT3954EUHE
Optional Circuit Components
1
1
C3
Cap., X5R 10µF 50V 20% 1210
Taiyo Yuden UMK325BJ106MM-T
2
0
C6-C8, C12-C15
Cap., 1210
Optional
3
0
C17
Cap., 0603
Optional
4
0
Q1
Diode, SOT23
Optional
5
1
R3
Res., Chip 499k 0.06W 1% 0603
Vishay CRCW0603499KFKEA
6
1
R4
Res., Chip 147k 0.06W 1% 0603
Vishay CRCW0603147KFKEA
7
1
R5
Res., Chip 1M 0.06W 1% 0402
Vishay CRCW04021M00FKED
8
1
R6
Res., Chip 165k 0.06W 1% 0402
Vishay CRCW0402165KFKED
9
1
R9
Res., Chip 100k 0.06W 5% 0603
Vishay CRCW0603100KJNEA
10
0
R10
Res., 0805
Optional
11
1
R11
Res., Chip 0Ω 0.33W 6A 0805
Vishay CRCW08050000ZOEA
12
1
R12
Res., Chip 0Ω 0.5W 10A 1206
Vishay CRCW12060000ZOEA
13
0
R13, R14, R16, R19, R20,
R23
Res., 0603
Optional
14
0
R15
Res., 1206
Optional
15
0
R17, R18, R22
Res., 0402
Optional
16
1
R24
Res., Chip 0Ω 0.25W 5A 0603
Vishay CRCW06030000Z0EA
1
9
E1-E5, E7, E8, E12, E13
Turret, Testpoint
Mill Max 2501-2-00-80-00-00-07-0
2
7
E6, E9-E11, E14-E16
Turret, Testpoint
Mill Max 2308-2-00-80-00-00-07-0
Hardware
dc2079af
6
E3
DIM
PWM
SYNC
CTRL
E6
C16
47nF
300Hz
INTVCC
R14
(Opt)
0603
SYNC
R16
(Opt)
0603
OUT
R15
(Opt)
1206
R6
165k
1%
124k
1%
0603
R21
R5
1M
R4
147k
1%
0603
R3
499k
0603
C10
0.01µF
2. CAPACITORS ARE 0603 CASE SIZE.
1. RESISTORS ARE 0402 CASE SIZE.
NOTES: UNLESS OTHERWISE SPECIFIED.
E15
E9
R20
(Opt)
0603
E14
E10
EN/UVLO
PGND
VIN
5V - 30V*
E2
OUT
R1
28.7k
1%
350kHz
(Opt)
0603
R13
R19
(Opt)
0603
OUT
C2
10µF
50V
1210
30
36
35
33
32
C9
4.7nF
R2
5.1k
2
1
31
C1
1µF
50V
1206
SYNC
C3
10µF
50V
1210
R12
0 Ohm
1206
DIM/SS
PWM
VREF
CTRL
VC
D1
PVIN
(Opt)
R18
PDS560-13
ISN
ISP
FB
INTVCC
VMODE
PWMOUT
U1
LT3954EUHE
EN/UVLO
SYNC
RT
L1
22µH
DR125-220
14
PVIN
PGND
15
E1
C13
(Opt)
1210
9
PGND
PVIN
5V - 30V*
10
NC
C12
8
SW
PGND
16
6
12
38
SW
PGND
17
VIN
GNDK
13
SW
GND
24
* SEE DEMO MANUAL FOR INPUT RANGE
PGND
21
SW
GND
37
20
SW
GND
4
(Opt)
1210
3
34
23
27
28
25
R22
(Opt)
RS1
C11
1µF
10V
0 Ohm
0603
100k
0603
0 Ohm
0805
R11
0.39
1%
1206
R24
INTVCC
-VMODE
(Opt)
0603
R23
37.4k
1%
R8
R7
1.00M
1%
0603
R9
C17
(Opt)
Q1
(Opt)
R17
(Opt)
SYNC
OUT
C5
4.7µF
50V
1210
(Opt)
0805
R10
M1
Si2318DS
C4
4.7µF
50V
1210
OUT
C6
(Opt)
1210
C14
(Opt)
1210
C7
(Opt)
1210
C15
(Opt)
1210
INTVCC
E16
E13
E12
E11
E8
E7
C8
(Opt)
1210 E4
E5
INTVCC
GND
GND
VMODE
LED-
LED+
32V LED MAX
650mA
PGND
OUT
DEMO MANUAL DC2079A
Schematic Diagram
dc2079af
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 DC2079A
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
dc2079af
8
Linear Technology Corporation
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●
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