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DESCRIPTION
DEMO MANUAL DC1831A
LT3763
High Power Constant Current,
Constant Voltage Synchronous
Buck Controller
Demonstration circuit 1831A is a high power constant
current, constant voltage synchronous buck controller
®
featuring the LT
3763. The input of the demo board is
up to 60V. The output is optimized for 10V, 10A as a
LED driver. As an LED driver, the output current is being
regulated until the output voltage reaches a programmed
voltage limit. The voltage limit on the demo board is set to
around 15V by R11 and R14. The load to be used with this
demo board is high current LEDs or laser diodes. Smaller
LEDs may not be able to handle the high current, even for
a short period of time. It is necessary to mount the LED
load on a proper heat sink. A fan may become necessary
to avoid exceeding LED’s maximum temperature rating.
The input voltage range of the LT3763 itself is 6V to 60V.
The demo board input range is 12V to 60V, therefore, the
demo board utilizes 80V MOSFETs. If an application has
a maximum input voltage of 48V, 60V MOSFETs such as
BSC100N06LS3, can be used for better efficiency at lower
voltage range. The typical efficiency of the demo board is
95% from a 24V input to a 10V, 10A load. The lower the
input voltage, the higher the efficiency tends to be for a given
load. At an output power level of 100W, even a one percent
efficiency improvement is a big advantage in minimizing
temperature rise. If an efficiency measurement is needed
in an application, the output voltage must be measured
at the output capacitors instead of at the LED load. This
prevents cable loss from being counted as a loss of the
board. The LT3763 turns off unnecessary circuits during
PWM off period to minimize power losses. As a result,
efficiency in many PWM dimming applications is high.
In most applications, input voltage reaching the maximum
specification is a transient event. However, a fan helps the
circuit to stay cool if running at or near peak input voltage
at full load in steady state. If running in steady state at
or near maximum input voltage and full load is required,
please contact LTC applications engineering.
The demo circuit 1831A achieves fast current rise time
from 0A to 10A. To see the real rise time, connecting wires
between the LED and the board should be as short as
possible to minimize the wire inductance and resistance.
The cathode of the LED should return to LED– with R17
populated with a resistor in a few mΩ. It is recommended
to measure the voltage on R17 with a short 50Ω coax cable
directly into a BNC connector on the oscilloscope. The
current can be calculated from the measured voltage. A
current probe adds more delays to the rise time so using
a current probe is not recommended. If fast rise time is
not required, the cathode of the LED can be connected to
GND as shown in Figure 2.
The LT3763 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 1831A.
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.
100
99
98
97
96
95
94
EFFICIENCY (%)
LED CURRENT = 10A
93
92
91
90
20
10
Figure 1. Demo Board Efficiency
LED CURRENT = 5A
40
30
VIN (V)
50
60
DN1831A F01
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DEMO MANUAL DC1831A
PERFORMANCE SUMMARY
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
V
OUT
I
OUT
f
SW
EFF Efficiency at DC I
Input Supply Range 12 60 V
Maximum Output Voltage 15 V
Output Current 9.4 10 10.6 A
Switching Frequency 380 430 480 kHz
(TA = 25°C)
= 10A, V
OUT
= 10V 95 %
OUT
QUICK START PROCEDURE
Demonstration circuit 1831A is easy to set up to evaluate the performance of the LT3763. Refer to Figure 2 for
proper measurement equipment setup and follow the
procedure below:
1. With power off, connect the input power supply to VIN
and GND. Note: make sure VIN is below 60V.
2. With power off, connect the LED load to VOUT and
GND (without PWM dimming) or VOUT and LED– (with
PWM dimming).
3. When measuring input and output voltage, measure at
test points TP1 to TP4.
4. Turn on the power at the input.
5. Carefully evaluate other design parameters as needed.
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QUICK START PROCEDURE
DEMO MANUAL DC1831A
Figure 2. Proper Measurement Equipment Setup
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DEMO MANUAL DC1831A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C1 Cap., Alum, 33μF,100V, 10.3x10.3 Sun Elect., 100CE33FS
2 2 C2, C5 Cap., X7R, 2.2μF, 100V, 10%, 1210 Murata, GRM32ER72A225KE35L
3 1 C6 Cap., X7R, 1μF, 100V, 10%, 1206 Murata, GRM31CR72A105KA01L
4 1 C7 Cap., X7R, 0.22μF, 10V, 10%, 0603 Murata, GRM188R71A224KA01D
5 2 C8, C10 Cap., POSCAP, 68μF, 16V Sanyo, 16TQC68MYF
6 2 C9, C11 Cap., X7R , 22μF, 25V, 10%, 1210 Murata, GRM32ER71E226KE15L
7 1 C12 Cap., X5R, 22μF, 6.3V,10%, 0805 Murata, GRM21BR60J226ME39L
8 1 C13 Cap., C0G, 2nF, 50V, 5%, 0603 Murata, GRM1885C1H202JA01D
9 2 C14, C19 Cap., X7R, 1000pF, 50V, 10%, 0603 AVX, 06035C102KAT2A
10 1 C15 Cap., X7R, 10nF,16V, 0603 Murata, GRM188R71C103KA01D
11 1 C17 Cap., X7R, 5.1nF, 10%, 25V, 0603 Murata, GRM188R71E512KA01
12 1 D1 1.0A Schottky Diode, DFLS160 Diodes/Zetex, DFLS160-7
13 1 D2 2.0A Schottky Diode, DFLS260 Diodes/Zetex, DFLS260-7
14 1 L1 Inductor, 2.8μH WE., 7443551280
15 4 Q1, Q2, Q3, Q4 MOSFET Renesas, RJK0851DPB
16 1 Q5 MOSFET Infineon, BSC014N03LS G
17 1 R1 Res., Chip, 374k, 1%, 0603 Vishay, CRCW0603374KFKEA
18 1 R2 Res., Chip, 124k, 1%, 0603 Vishay, CRCW0603124KFKEA
19 6 R3, R5, R8, R24, R25, R27 Res., Chip, 100k, 1%, 0603 Vishay, CRCW0603100KFKEA
20 1 R4 Res., Chip, 0.005Ω, 1W, 1%, 2512 Vishay, WSL25125L000FEA
21 1 R7 Res., Chip, 45.3k, 1%, 0603 Vishay, CRCW060345K3FKEA
22 1 R11 Res., Chip, 5.62k, 1%, 0603 Vishay, CRCW06035K62FKEA
23 1 R12 Res., Chip, 680K, 1%, 0603 Vishay, CRCW0603680KFKEA
24 1 R14 Res., Chip, 487Ω, 1%, 0603 Vishay, CRCW0603487RFKEA
25 1 R15 Res., Chip, 30.9k, 1%, 0603 Vishay, CRCW060330K9FKEA
26 1 U1 I.C. LT3763EFE, 20-Pin TSSOP Linear Tech., LT3763EFE
Additional Demo Board Circuit Components
1 0 C3, C4 Cap., 1210, Opt
2 0 C16, C18, C20 Cap., 0603, Opt
3 2 R6, R17 Res., Chip, 0Ω, 2512 Vishay, CRCW25120000Z0EG
4 0 R9, R20, R21 Res., 1206, Opt
5 8 R10, R13, R16, R18, R19, R22,
R23, R26
Hardware–For Demo Board Only
1 5 J1, J2, J3, J4, J5 Jack, Banana Keystone, 575-4
2 10 E1-E8, E10, E11 Testpoint, Turret, 0.094" Mill-Max, 2501-2-00-80-00-00-07-0
3 4 Stand-Off, Nylon 0.5" tall Keystone, 8833 (Snap On)
Res., Chip, 0Ω, 0603 Vishay, CRCW06030000Z0ED
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SCHEMATIC DIAGRAM
DEMO MANUAL DC1831A
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.
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DEMO MANUAL DC1831A
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
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
dc1831af
LT 1012 • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2012
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