DC2020A - Demo Manual

DEMO MANUAL DC2020A
LT3955EUHE
60VIN 80VOUT LED Driver
Description
Demonstration circuit 2020A is a 60VIN, 80VOUT 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 60V and drives up to 67V of LEDs at 300mA (when
PVIN is less than VLED). DC2020A 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 320Hz for
DC2020A). The PWMOUT duty cycle is determined by the
voltage on the DIM terminal. Between 0V and 7.7V VDIM
gives between 4% and 96% PWM duty cycle. Information
regarding PWM dimming ratios and performance can be
found in the LT3955 data sheet in the applications section. Analog dimming is also simple to use with a single
voltage source on the CTRL terminal.
DC2020A features high efficiency at 350kHz switching
frequency. At high LED string voltages up to 67V and
300mA of LED current, the single switch controller has
92% efficiency. The LT3955 has an internal 80V, 3.5A
switch that simplifies the schematic and layout.
Modifications can be made to DC2020A 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 LT3955 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 75V if the LED string is opened
although it may reach 79V 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 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 5V.
DC2020A PWM dimming is simplified when compared
with other LED drivers. The LT3955 generates its own
PWMOUT dimming waveform at a frequency determined
The LT3955 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 DC2020A. The LT3955EUHE
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 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.
dc2020afa
1
DEMO MANUAL DC2020A
Performance Summary
Specifications are at TA = 25°C
PARAMETER
CONDITIONS
VALUE (TYPICAL)
Input Voltage PVIN Range
Operating
5V to VLED (up to 60V)
Switching Frequency
R1 = 28.7k
350kHz
ILED
RS1 = 0.82Ω 9V < PVIN < VLED (60V)
300mA
Low PVIN ILED (CTRL foldback)
RS1 = 0.82Ω PVIN = 7.0V
RS1 = 0.82Ω PVIN = 8.0V
240mA
278mA
VLED Range
R7 = 1M R8 = 16.9k
PVIN < VLED < 67V
Open LED Voltage
R7 = 1M R8 = 16.9k
75V
Typical Efficiency
92.1%
PVIN Under Voltage Lockout (falling turn-off)
PVIN = 14V VLED = 67V ILED = 300mA PWM = INTVCC
R3 = 499k and R4 = 165k
PVIN Under Voltage Lockout (rising turn-on)
R3 = 499k and R4 = 165k
6.1V
INTVCC
Operating
7.85V
Peak Switch Current Limit
5.0V
3.3A
PWMOUT Dimming Duty Cycle
VDIM = 7.7V
VDIM = 4.0V
VDIM = 1.5V
VDIM = 0.4V
96%
50%
10%
4.3%
Internal PWM Dimming Frequency
C16 = 0.047µF 0V < VDIM < 8V
300Hz
Quick Start Procedure
Demonstration circuit DC2020A is easy to set up to
evaluate the performance of the LT3955EUHE. Follow the
procedure below:
1. Connect a string of LEDs that will run with forward
voltage less than or equal to 67V, but greater than the
intended PVIN, to the LED+ and LED– terminals on the
PCB as shown in Figure 1.
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 60V (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.
2
5. Turn the input power supply on and make sure the
voltage is between 6.1V and 60V (or VLED) to start.
6. Release the EN/UVLO-to-GND connection.
7. Observe the LED string running at the programmed
LED current and brightness related to the programmed
PWMOUT duty cycle.
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.
dc2020afa
DEMO MANUAL DC2020A
Quick Start Procedure
IIN
–
+
–
VIN
+
+
–
PVIN
OPTIONAL FOR SHUTDOWN
+
VOUT
–
+
+
–
VDIM
0V TO 7.7V
ILED
–
+
67V LED
300mA
dc2020A F02
OPTIONAL
FOR
ANALOG
DIMMING
–
OPTIONAL
FOR
EXTERNAL
PWM
DIMMING
Figure 1. Test Procedure Setup Drawing for DC2020A
dc2020afa
3
DEMO MANUAL DC2020A
Quick Start Procedure
100%
98%
67VLED 300mA PWM = INTVCC
EFFICIENCY
96%
94%
92%
90%
88%
86%
84%
82%
80%
0
5
10
15
20
25
30
35
40
45
50
PVIN (V)
55
60
dc2020a F02
Figure 2. DC2020A Efficiency with 67V LEDs at 300mA and 100% PWMOUT Duty Cycle
VDIM = 8V
DCPWM = 97.2%
VDIM = 3.87V
DCPWM = 50%
ILED
0.3A/DIV
VDIM = 1.47V
DCPWM = 10%
VIN = 24V
VLED = 65V
0.5ms/DIV
dc2020a F03
VDIM = 0V
DCPWM = 2.8%
Figure 3. DC2020A 300Hz PWM Dimming Waveforms at Different PWMOUT Duty Cycles
4
dc2020afa
DEMO MANUAL DC2020A
Quick Start Procedure
0.350
0.300
ILED (A)
0.250
0.200
0.150
UNDER0.100 VOLTAGE
LOCKOUT
0.050 (FALLING)
TURN-ON
(RISING)
0.000
4
5
6
7
8
PVIN (V)
9
10
11
12
dc2020a F04
Figure 4. DC2020A CTRL LED Current Foldback at Low PVIN with UVLO (Falling and Rising)
dc2020afa
5
DEMO MANUAL DC2020A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
CAP, 1206, 1µF, 20%, 100V, X7R
TDK C3216X7R2A105MT
Required Circuit Components
1
1
C1
2
2
C2, C3
CAP, 1210, 4.7µF, 10%, 100V, X7S
TDK C3225X7S2A475K
3
4
C4, C5, C6, C7
CAP, 1210, 2.2µF, 20%, 100V, X7R
TDK C3225X7R2A225M
4
0
C8, C14, C15
CAP, 1210, 2.2µF, 20%, 100V, X7R, OPTION TDK C3225X7R2A225M OPTION
5
1
C9
CAP, 0603, 4.7nF, 20%, 25V, X7R
AVX 06033C472MAT2A
6
1
C10
CAP, 0603, 0.01µF, 10%, 25V, X7R
AVX 06033C103KAT2A
7
1
C11
CAP, 0603, 1µF, 10%, 10V, X7R
Taiyo Yuden LMK107BJ105KA
8
1
C16
CAP, 0603, 47nF, 20%, 16V, X7R
Taiyo Yuden EMK107BJ473MA
9
1
D1
DIODE, SCHOTTKY
DIODES INC. PDS3100-13
10
1
L1
IND, 22µH, 20%
COOPER COILTRONICS DR125-220
11
1
M1
MOSFET N-CHANNEL 100V
VISHAY SILICONIX Si2328DS
12
1
RS1
RES, 1206, 0.82Ω, 1%, 1/4W
IRC LR1206LF-01-R820FT
13
1
R1
RES, 0402, 28.7kΩ, 1%, 1/16W
VISHAY CRCW040228K7FKED
14
1
R2
RES, 0402, 5.1kΩ, 5%, 1/16W
VISHAY CRCW04025K10JNED
15
1
R3
RES, 0603, 499kΩ, 1%, 1/16W
VISHAY CRCW0603499KFKEA
16
1
R4
RES, 0402, 165kΩ, 1%, 1/16W
VISHAY CRCW0402165KFKED
17
1
R5
RES, 0402, 1MΩ, 1%, 1/16W
VISHAY CRCW04021M00FKED
18
1
R6
RES, 0603, 147kΩ, 1%, 1/16W
VISHAY CRCW0603147KFKEA
19
1
R7
RES, 0603, 1MΩ, 1%, 1/16W
VISHAY CRCW06031M00FKEA
20
1
R8
RES, 0402, 16.9kΩ, 1%, 1/16W
VISHAY CRCW040216K9FKED
21
1
R9
RES, 0603, 100kΩ, 5%, 1/16W
VISHAY CRCW0603100KJNED
22
1
R21
RES, 0402 124kΩ, 1% 1/16W
VISHAY CRCW0402124KFKED
23
1
U1
IC, 60VIN/80VOUT LED DRIVER
LINEAR TECH. LT3955EUHE
Optional Electrical Components
1
0
C12, C13
CAP, 1210 OPTION
2
0
C17
CAP., 0603 OPTION
3
0
Q1
XSTR, OPTION
OPTION
OPTION
4
0
R10
RES, 0805, OPTION
OPTION
5
1
R11
RES, 0805, 0Ω, JUMPER
VISHAY CRCW08050000Z0EA
6
1
R12
RES, 1206, 0Ω, JUMPER
VISHAY CRCW1206000Z
7
0
R13, R14, R16, R19, R20, R23
RES, 0603 OPTION
OPTION
8
0
R15
RES, 1206 OPTION
OPTION
9
0
R17, R18, R22
RES, 0402 OPTION
OPTION
10
1
R24
RES, 0603, 0Ω JUMPER
VISHAY CRCW06030000Z0EA
Optional Hardware
1
9
E1, E2, E3, E4, E5, E7, E8, E12, E13
TURRET
MILL MAX 2501-2-00-80-00-00-07-0
2
7
E6, E9, E10, E11, E14, E15, E16
TURRET
MILL MAX 2308-2-00-80-00-00-07-0
6
dc2020afa
E3
DIM
PWM
SYNC
CTRL
E6
E15
E9
R20
OPT
0603
E14
E10
EN/UVLO
PGND
VIN
5V - 60V*
E2
R6
147k
1%
R4
165k
1%
0603
R3
499k
0603
124k
1% C10
0.01µF
R21
R5
1M
2. CAPACITORS ARE 0603 CASE SIZE.
1. RESISTORS ARE 0402 CASE SIZE.
NOTES: UNLESS OTHERWISE SPECIFIED.
C16
47nF
300Hz
INTVCC
R14
OPT
0603
SYNC
R16
OPT
0603
OUT
R15
OPT
1206
OUT
R1
28.7k
350kHz
30
36
35
33
32
31
2
1
C9
4.7nF
R2
5.1k
SYNC
C1
1µF
100V
1206
C3
4.7µF
100V
1210
OPT
0603
R13
R19
OPT
0603
OUT
C2
4.7µF
100V
1210
R12
0
1206
VC
RT
DIM/SS
PWM
VREF
CTRL
PVIN
OPT
R18
D1
PDS3100-13
ISN
ISP
FB
INTVCC
VMODE
PWMOUT
U1
LT3955EUHE
EN/UVLO
SYNC
L1
22µH
14
PVIN
PGND
E1
OPT
1210
C13
9
PGND
15
6
OPT
8
SW
PGND
16
PVIN
5V - 60V*
10
NC
1210
38
SW
PGND
17
VIN
GNDK
12
SW
GND
24
* SEE DEMO MANUAL FOR INPUT RANGE
PGND
13
21
SW
GND
37
20
SW
GND
4
C12
3
34
23
27
28
25
R22
OPT
C11
1µF
10V
0603
R9 100k
C17
OPT
Q1
OPT
R17
OPT
INTVCC
-VMODE
OPT
0603
R23
16.9k
1%
R8
R7
1.00M
1%
0603
0
0603
R24
0
0805
R11
0.82 1%
1206
RS1
OUT
SYNC
C5
2.2µF
100V
1210
OPT
0805
R10
M1
Si2328DS
C4
2.2µF
100V
1210
OUT
C6
2.2µF
100V
1210
C14
OPT
1210
C7
2.2µF
100V
1210
C15
OPT
1210
INTVCC
PGND
OUT
E16
E13
E12
E11
E8
INTVCC
GND
GND
VMODE
LED-
E7 LED+
67V LED MAX
300mA
C8
OPT
1210 E4
E5
DEMO MANUAL DC2020A
Schematic Diagram
dc2020afa
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 DC2020A
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
8
dc2020afa
Linear Technology Corporation
LT 0413 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2013
Similar pages