DEMO MANUAL DC1428A
LT3645
0.5A, 36V Step-Down
Regulator with LDO
DESCRIPTION
Demonstration circuit 1428A features the LT®3645. The
circuit is designed to convert a 5V to 36V input source to
3.3V at 300mA and 2.5V at 200mA. JP1 and JP2 enable and
disable the 3.3V output and the 2.5V output respectively.
LDO only operates if both, EN/UVLO and EN2 are greater
than 1.2V. Demo board includes an optional resistor, R8,
for easy implementation of UVLO. The LT3645 data sheet
gives a complete description of the part, its operation and
PERFORMANCE SUMMARY
SYMBOL
PARAMETER
VIN
Input Supply Range
3.3VOUT
Buck Output Voltage Accuracy
2.5VOUT
LDO Output Voltage Accuracy
application information. The data sheet must be read in
conjunction with this quick start guide for working on or
modifying the demo circuit 1428A.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
(TA = 25°C)
CONDITIONS
TYP
5
MAX
V
V
3.226
3.3
3.374
VIN = 5V to 36V, ILOAD = 200mA
2.444
2.5
2.556
83
UNITS
36
VIN = 5V to 36V, ILOAD = 500mA
VIN = 5V, ILOAD = 500mA for Buck, 0mA for LDO
Efficiency
MIN
V
%
VIN = 5V, ILOAD = 300mA for Buck, 200mA for LDO
75
%
Buck VOUT Ripple
VIN = 5V, ILOAD = 500mA
10
mV
LDO VOUT Ripple
VIN = 5V to 36V, ILOAD = 200mA
1
mV
750
kHz
fS
Switching Frequency
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DEMO MANUAL DC1428A
QUICK START PROCEDURE
Demonstration circuit 1428A is easy to set up to evaluate
the performance of the LT3645. Refer to Figures 1 and 2
for proper measurement equipment setup and follow the
procedure below:
To measure the input or output voltage ripple, care must
be taken to avoid a long ground lead on the oscilloscope
probe. Measure the input or output voltage ripple by touching the probe tip directly across the VIN or VOUT and GND
terminals. See Figure 2 for proper scope probe technique.
2. With power off, connect the input power supply to VIN
and GND. Apply 5V to input and check for the proper
output voltages.
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
Once the proper output voltage is established, adjust the
load within the operating range and observe the output
voltage regulation, ripple voltage, efficiency and other
parameters.
1. Place jumpers in the following position:
JP1 ON
JP2 ON
Efficiency VOUT = 3.3V
90
EFFICIENCY (%)
80
70
60
50
VIN = 7V
VIN = 12V
VIN = 24V
0
100
200
300
400
LOAD CURRENT (mA)
500
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DEMO MANUAL DC1428A
Figure 1. DC1428A Proper Equipment Set-Up
GND
VOUT
Figure 2. Proper Input/Output Ripple Measurement Technique
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DEMO MANUAL DC1428A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
1
C1
Capacitor, X7R, 0.1μF, 10V, 10%, 0603
AVX, 0603ZC104KAT2A
2
1
C2
Capacitor, Tantalum, 10μF, 63V
Suncon, 63CE10BS
3
1
C3
Capacitor, X7R, 1μF, 50V, 10%, 1206
Murata, GCM31MR71H105KA55L
4
1
C4
Capacitor, X5R, 10μF, 6.3V, 0805
AVX, 08056D106MAT2A
5
1
C5
Capacitor, X5R, 2.2μF, 6.3V, 10%, 0603
AVX, 06036D225KAT2A
6
1
D1
Schottky Barrier Rect., 1A, power, DI323
Diodes Inc. PD3S140
7
1
L1
Inductor 10μH
Taiyo Yuden, NRH3012T100MN
8
2
R1, R4
Resistor, 10k, 1/16W, 5%, 0402
Vishay, CRCW040210K0JNED
9
1
R2
Resistor, 31.6k, 1/16W, 1%, 0402
Vishay, CRCW040231K6FKED
10
2
R3, R7
Resistor, 10k, 1/16W, 1%, 0402
Vishay, CRCW040210KFKED
11
1
R5
Resistor, 21.5k, 1/16W, 1%, 0402
Vishay, CRCW040221K5FKED
12
1
R6
Resistor, 100k, 1/16W, 5%, 0402
Vishay, CRCW04021003JKED
13
1
U1
IC, LT3645EMSE
Linear Technology, LT3645EMSE
14
1
Fab, Printed Circuit Board
Demo Circuit 1428A
Additional Demo Board Circuit Components
1
2
C11, C12
Capacitor, X7R, 0.1μF, 10V, 10%, 0603
2
0
C13 (OPT)
Capacitor, 0402
3
0
R8 (OPT)
Resistor, 0402
AVX, 0603ZC104KAT2A
Hardware/Components (For Demo Board Only)
1
7
E1-E7
Testpoint, Turret, 0.094"
Mill-Max, 2501-2-00-80-00-00-07-0
2
2
JP1, JP2
Header, 3-Pin, 1 Row, 0.079CC
Samtec, TMM-103-02-LS
3
2
XJP1, XJP2
Shunt, 0.079" Center
Samtec, 2SN-BK-G
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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.
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DEMO MANUAL DC1428A
SCHEMATIC DIAGRAM
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DEMO MANUAL DC1428A
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 0611 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
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