Page 1
Description
DEMO MANUAL DC1772A
LT3761EMSE
High Voltage LED Controller
with Internal PWM Dimming
DC1772A is a high voltage LED controller with internal
PWM dimming. It generates its own PWMOUT waveform
for accurate PWM dimming with up to 25:1 brightness
ratio. It accepts an input voltage from 8V to 60V (8V UVLO
and 9.1V rising turn-on), and drives up to 60V of LEDs
at 1A (when PVIN is less than V
both PWM and analog dimming of the LED string. It has
an OPENLED flag that indicates when the LED string has
been removed.
DC1772A features high efficiency at 350kHz switching
frequency. At high LED string voltages up to 60V and
1A of LED current, the single switch controller has 94%
efficiency. The open LED overvoltage protection uses
the IC’s constant voltage regulation loop to regulate the
output to approximately 69.8V if the LED string is opened
although it may reach 74V peak during transient from
running LEDs to open. The maximum LED string voltage
can be raised from 60V to 65V (or higher) with a simple
change of feedback resistors.
For low input voltage operation, the CTRL pin voltage is
reduced as the input voltage drops below
LED brightness and restraining the peak switch currents
in order to limit inductor and switch size. UVLO turns the
LEDs off when PVIN drops below 8V.
). DC1772A features
LED
10V, reducing
by the capacitance on the PWM pin (C8 gives 300Hz for
DC1772A). 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 LT3761 data sheet in the Applications Infor
mation section. Analog dimming is also simple to use with
a single voltage source on the CTRL terminal.
Modifications can be made to DC1772A 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 the LT3761 data sheet for details. It can be
modified to provide LED+ to GND short-circuit protection
as well.
The LT3761 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 DC1772A. The LT3761EMSE is
assembled in a 16-lead plastic MSOP MSE package with
a thermally
is essential for maximum thermal performance. See the
data sheet section Layout Considerations.
enhanced ground pad. Proper board layout
-
DC1772A PWM dimming is simplified when compared
with other LED drivers. The LT
PWMOUT dimming waveform at a frequency determined
®
3761 generates its own
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.
dc1772af
1
Page 2
DEMO MANUAL DC1772A
performance summary
PARAMETER CONDITION VALUE (TYPICAL)
Input Voltage PVIN Range Operating 8V to V
Switching Frequency R6 = 29.4k 350kHz
I
LED
Low PVIN I
Range R3 = 1M R4 = 18.2k PVIN < V
V
LED
Open LED Voltage R3 = 1M R4 = 18.2k 69.8V
Typical Efficiency PVIN = 14V V
PVIN Under Voltage Lockout (Falling Turn-Off) R1 = 499k and R2 = 90.9k 8V
PVIN Under Voltage Lockout (Rising Turn-On) R1 = 499k and R2 = 90.9k 9.1V
INTVCC Operating 7.85V
Peak Switch Current Limit RS1 = 0.008Ω 12.5A
PWMOUT Dimming Duty Cycle VDIM = 7.7V
Internal PWM Dimming Frequency C8 = 0.047µF 0V < VDIM < 7.7V 300Hz
(CTRL Foldback) RS2 = 0.25Ω PVIN = 8.5V
LED
Specifications are at TA = 25°C
RS2 = 0.25Ω 10V < PVIN < V
RS2 = 0.25Ω PVIN = 9V
= 60V I
LED
VDIM = 4V
VDIM = 1.5V
VDIM = 0.4V
LED
= 1A PWM = INTVCC 94%
LED
(Up to 60V)
LED
(60V) 1A
930mA
975mA
< 60V
LED
96%
50%
10%
4.3%
Quick start proceDure
Demonstration circuit 1772A is easy to set up to evaluate
the performance of the LT3761EMSE. Follow the proce
dure below:
1. Connect a string of LEDs that will run with forward volt
age less than 60V, but greater than 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 V
4. Connect the DIM terminal to a voltage between 0V and
7.7V 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.
LED
).
5. Turn the input power supply on and make sure the
-
voltage is between 8V and 60V (or V
LED
).
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 7.7V 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.
2
dc1772af
Page 3
Quick start proceDure
DEMO MANUAL DC1772A
Figure 1. Test Procedure Setup Drawing for DC1772A
dc1772af
3
Page 4
DEMO MANUAL DC1772A
1A/DIV
0.5ms/DIV
= 4.3%
Quick start proceDure
100%
98%
96%
94%
92%
90%
88%
EFFICIENCY (%)
86%
84%
82%
80%
60VLED 1.0A PWM = INTVCC
0V 5V 10V 15V 20V 25V 30V 35V 40V 45V 50V 55V 60V
PVIN INPUT VOLTAGE (V)
Figure 2. DC1772A Efficiency with 60V LEDs at 1A and 100% PWMOUT Duty Cycle
V
= 7.7V
DIM
= 96%
DC
PWM
V
= 4V
DIM
= 50%
DC
I
LED
V
DC
V
DC
DIM
DIM
PWM
= 1.5V
PWM
= 0.4V
PWM
= 10%
Figure 3. DC1772A 300Hz PWM Dimming Waveforms at Different PWMOUT Duty Cycles
4
dc1772af
Page 5
Quick start proceDure
1.2
1.0
0.8
0.6
ILED (A)
0.4
0.2
0.0
under
voltage
lockout
(falling)
7.5 8 8.5 9 9.5 10 10.5 11 11.5 12
Figure 4. DC1772A CTRL LED Current Foldback at Low PVIN with UVLO Falling and Rising
DEMO MANUAL DC1772A
turn-on
(rising)
PVIN (V)
dc1772af
5
Page 6
DEMO MANUAL DC1772A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C1, C10 Cap., X7S 4.7µF 100V 10% 1210 TDK C3225X7S2A475K
2 4 C2, C3, C11, C12 Cap., X7R 2.2µF 100V 10% 1210 TDK C3225X7R2A225K
3 1 C4 Cap., X7R 1µF 100V 20% 1206 TDK C3216X7R2A105M
4 1 C5 Cap., X5R 1µF 10V 10% 0603 AVX, 0603ZD105K AT2A
5 1 C6 Cap., X7R 4700pF 25V 20% 0603 AVX, 06033C472M ATAT2A
6 1 C7 Cap., X5R 0.01µF 16V 20% 0603 AVX, 0603YD103MAT 2A
7 1 C8 Cap., X7R 0.047µF 50V 10% 0603 AVX, 06035C473K AT2A
8 1 D1 Schottky Diode 5A PowerDi5 Diodes Inc. PDS5100H
9 1 L1 Inductor, 10µH HC9-SERIES/COOPER Cooper Bussmann, HC9-100-R
10 1 M1 MOSFET N-Chan., 100V Infineon, BSC123N08NS3G
11 1 M2 MOSFET N-Chan., 100V Siliconix Si2328DS-T1-GE3
12 1 RS1 Res., Chip., 0.008Ω 1/2W 1% 2010 Vishay WSL20108L000FEA
13 1 RS2 Res., Chip., 0.25Ω 1/2W 1% 1206 Vishay WSL1206R2500FEA
14 1 R1 Res., Chip, 499k 0.06W 1% 0402 Vishay CRCW0402499KFKED
15 1 R2 Res., Chip, 90.9k, 0.06W 1% 0402 Vishay CRCW040290K9FKED
16 1 R3 Res., Chip, 1M, 0.1W 1% 0603 Vishay CRCW06031M00FKED
17 1 R4 Res., Chip, 18.2k, 0.06W 1% 0402 Vishay CRCW040218K2FKED
18 1 R5 Res., Chip 10k, 0.06W 5% 0402 Vishay CRCW040210K0JKED
19 1 R6 Res., Chip, 29.4k, 0.06
20 1 R7 Res., Chip 1M, 0.06W 5% 0402 Vishay CRCW04021M00JKED
21 1 R8 Res., Chip, 140k, 0.06W 1% 0402 Vishay CRCW0402140KFKED
22 1 R9 Res., Chip 100k, 0.1W 5% 0603 Vishay CRCW0603100KJKEA
23 1 R10 Res., Chip, 124k, 0.1W 1% 0603 Vishay CRCW0603124KFKED
24 1 U1 I.C., LED Driver MSOP(16)-MSE Linear Tech. Corp. LT3761EMSE
Optional Electrical Components
1 0 C9, C13(OPT) Cap., 1210
2 0 C14, C15 (OPT) Cap., 0603
3 0 D2 (OPT) Rectifier, ESIC SMA
4 0 D3 (OPT) Diode, 1N4148W, SOD-123
5 0 M3 (OPT) MOSFET N-Chan., SOT23 (OPT)
6 0 M4 (OPT) MOSFET P SO8-PWR (OPT)
7 0 Q1, Q2, Q3 (OPT) PNP SOT23 (OPT)
8 1 R11 Res., Chip, 0Ω, 1206 Vishay CRCW12060000Z0EA
9 1 R12 Res., Chip 0Ω, 0603 Vishay CRCW06030000Z0ED
10 0 R13, R17, R19-22 (OPT) Res., 0402
11 0 R14, R24 (OPT) Res., 0805
12 0 R15 (OPT) Res., 1206
13 0 R16, R18, R23, R25-R27 (OPT) Res., 0603
Optional Hardware
1 14 E1-E14 Turret, Testpoint Mill Max 2501-2-00-80-00-00-07-0
W 1% 0402 Vishay CRCW040229K4FKED
6
dc1772af
Page 7
schematic Diagram
DEMO MANUAL DC1772A
D1
10uH
10uH
HC9-100-R
HC9-100-R
1A
LED +
60VLED
LED +
60VLED
D2
OPTD2OPT
OPTM4OPT
M4
OPT
R14
R14
OUT
1%
1%
RS2
RS2
0.25
0.25
1206
1206
1/2W
1/2W
OPT
OPT
C13
1210
C13
1210
C12
100V
1210
C12
100V
1210
2.2uF
2.2uF
2.2uF
2.2uF
C11
100V
1210
C11
100V
1210
OUT
C3
2.2uF
100V
1210
C3
2.2uF
100V
1210
C2
2.2uF
100V
1210
C2
2.2uF
100V
1210
PDS5100HD1PDS5100H
M1
COOPER
COOPER
0
0
R11
R11
1206
1206
4.7uF
100V
1210
4.7uF
100V
1210
C1
C1
OPT
OPT
0805
OPT
0805
Q2
OPT
Q2
OPT
R3
1.0M1%0603R31.0M1%0603
RS1
RS1
BSC123N08NS3M1BSC123N08NS3
0603
0603
R25
R25
SOT23
SOT23
C15
C15
OPENLED
M3
1uF
1uF
FB
0.008
0.008
100V
100V
OPT.
OPT.
15
16
14
R4
R4
2010
2010
1206
1206
OPTM3OPT
18.2k
18.2k
2
FB
SENSE
GATE
VIN
12
R13
R13
C4
C4
OUTOUT
OPTIONAL for BUCK MODE
C9
C9
OPT
OPT
1210
1210
L1
L1
OPTIONAL for SHORT CIRCUIT
OPT
OPT
1%
1%
4
EN/UVLO
VREF7CTRL
LED -LED -
R24
R24
0805
0805
OPT
OPT
M2
Si2328DSM2Si2328DS
0603
0603
0
0
R12
R12
0603
0603
R23
R23
OPT
OPT
C14
C14
OPT
OPT
3
1
ISP
ISN
U1
8
PWMOUT
LT3761EMSEU1LT3761EMSE
6
R22
R22
OPT
OPT
INTVCC
9
13
GNDGND
PWMPWM
Q1
Q1
R20
R20
R27
R27
1%R629.4k
1%
10kR510k
PVIN
R26
R26
OPT
OPT
C7
OPT
OPT
OPT
OPT
0603
0603
350kHz
C6
C6
SOT23
SOT23
OPT
OPT
LED+
D3
0603
0603
4700pF
4700pF
0.01uFC70.01uF
FB
OPTIONAL LEVEL SHIFT for BUCK
MODE or BUCK-BOOST MODE
OPTD3OPT
OPTIONAL for SHORT CIRCUIT
R19
R19
OPT
OPT
OUT
R21
R21
OPT
OPT
FB
Q3
Q3
OPT
OPT
SOT23
SOT23
INTVCC
R18
0603
R18
0603
OPT
OPT
INTVCC
C8
0.047uFC80.047uF
R6
29.4k
11
PWM
RT
17
GND
R5
5
VC
10
DIM/SS
OPENLED
PVIN
PVIN
PVIN
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.
8V - 60V
8V - 60V
124k
124k
0603
0603
R10
1%
8V - 60V
8V - 60V
1%
499k
499k
OPT
OPT
0603
EN/UVLOEN/UVLO
R2
1%
90.9kR290.9k
R7
R17
R17
R8
1M
1%R71M
1%
OPT
OPT
OUT
CTRLCTRL
140k
1%R8140k
1%
INTVCCINTVCC
C5
C5
10V
10V
1uF
1uF
R9
100k
R1
R1
R16
R16
OUT
PGNDPGND
4.7uF
100V
1210
4.7uF
100V
1210
C10
C10
1206
R15
R15
OPT
OPT
OUT
VIN
VIN
R10
0603R9100k
0603
RESISTORS ARE IN 0402.
CAPACITORS ARE IN 0603.
NOTE: UNLESS OTHERW ISE SPECIFIED
DIMDIM
GNDGND
OPENLEDOPENLED
dc1772af
7
Page 8
DEMO MANUAL DC1772A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LT C ) 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 LT C 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 LT C 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.
LT C 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
Linear Technology Corporation
8
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
dc1772af
LT 1012 • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2012
Loading...