DC736A - Demo Manual

DEMO MANUAL DC736A
LT3724
High Voltage Current Mode
Step-Down Converter
Description
Demonstration Circuit 736A is a 200kHz high voltage,
current-mode DC/DC step-down converter featuring the
LT®3724.
The circuit operates from a VIN range of 30V to 55V and
outputs 24V at 3A (72W). A soft-start feature controls
the output voltage slew rate at start-up, reducing current
surges and voltage overshoots. Burst Mode® operation
that improves the efficiency at light loads can be enabled
with a jumper.
An optional boost bias circuit is provided on the bottom
side of the board for back-driving the LT3724 internal
regulator from the output voltage. Customers might want
to use this optional circuit with modified applications that
have relatively high input voltages and low (~5V) output
voltages. In such applications, the optional circuit can
increase the overall efficiency by reducing the power lost
Performance Summary
PARAMETER
This circuit is suitable for a wide range of Industrial control
systems and particularly suitable for 12V/42V automotive
applications and 48V Telecom power supplies.
The LT3724 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this demo manual.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
Specifications are at TA = 25°C
CONDITIONS
Input Voltage Range
Efficiency
in the LT3724. The demonstration circuit has also been
layed out with the option for a second switching MOSFET
to facilitate higher output currents. The circuit design can
be modified for a boost converter configuration.
MIN
TYP
30
VIN = 30V, IOUT = 3.0A
VIN = 48V, IOUT = 3.0A
VIN = 55V, IOUT = 3.0A
Switching Frequency
MAX
55
UNITS
V
97.4
95.4
94.7
%
%
%
200
kHz
Output Voltage
IOUT = 0A to 3.0A
24
V
Output Voltage Ripple
VIN = 48V, IOUT = 3.0A
100
mV
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DEMO MANUAL DC736A
Quick Start Procedure
DC736A is easy to set up to evaluate the performance of
the LT3724. Refer to Figure 1 for proper measurement
equipment setup and follow the procedure below:
5.Turn on the power at the input and adjust the input
voltage until the LT3724 turns on.
NOTE: Make sure that the input voltage does not exceed
55V.
NOTE: When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the oscilloscope probe. See Figure 2 for the proper scope technique.
6.Check for the proper output voltage.
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high or
is shorted.
1.Place JP1 in the RUN position.
2.Place JP2 in the desired operating mode: fixed frequency
or Burst Mode operation.
7.Once the proper output voltage is established, adjust the
input voltage and load within the operating range and
observe the output voltage regulation, ripple voltage,
efficiency and other parameters.
3.With power off, connect the input power supply to VIN
and GND.
4.With power off, connect the load to VOUT and GND.
55V
Power
Supply
+
–
–
LOAD
–
+
–
+
+
Figure 1. Proper Measurement Equipment Setup
+
VOUT
–
COUT
GND
Figure 2. Measuring Output Ripple
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DEMO MANUAL DC736A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
1
1
CIN1
Cap., Aluminum 68µF 63V 20%
Sanyo 63MV68AX-T
2
2
CIN2, CIN3
Cap., X7R 2.2µF 100V 20%
TDK C4532X7R2A225M
3
1
COUT1
Cap., Alum 330µF 35V 10%
Sanyo 35CV330AX-T
4
2
COUT3, COUT2
Cap., X7R 22µF 25V 20%
TDK C5750X7R1E226M
5
1
C1
Cap., NPO 1000pF 100V 10%
AVX 08051A102KAT1A
6
1
C2
Cap., X5R 0.22µF 16V 10%
Taiyo Yuden EMK107BJ224KA
7
1
C3
Cap., X7R 1000pF 25V 10%
AVX 04023C102KAT2A
8
1
C4
Cap., X5R 0.1µF 16V 10%
AVX 0402YD104KAT2A
9
1
C5
Cap., X5R 1µF 16V 10%
Taiyo Yuden EMK212BJ105KG
10
1
C6
Cap., X7R 120pF 25V 10%
AVX 04023C121KAT2A
11
1
C7
Cap., X7R 1500pF 16V 20% 0402
AVX 0402YC152MAT2A
12
1
C12
Cap., X7R 0.01µF 16V 10%
AVX 0402YC103KAT2A
13
1
D1
Diode, Speed Switching
Diodes Inc. BAS19
14
1
D2
Schottky Diode 60V
IR 30BQ060
15
1
D5
Diode, 75V/200mW
Diodes Inc. 1N4148WS
16
1
L1
Inductor, 47µH
Coilcraft DO5040H-473MLB
17
1
Q1
MOSFET N-Channel, PowerPak SO8
Vishay Siliconix Si7852DP
18
1
R1
Res, Chip 1M 0.1W 5%
AAC CR10-105JM
19
1
R2
Res/Jumper, Chip 0Ω 0.06W 1A
AAC CJ05-000M
20
1
R3
Res., Chip 52.3k 1/16W 1%
Vishay CRCW0402 52.3K 1%
21
1
R4
Res., Chip 402K 1/16W 1%
AAC CR05-4023FM
22
1
R5
Res., 0.025 0.5W 1%
IRC LRF2010-01-R025-F
23
1
R6
Res., Chip 1M 0.1W 5%
AAC CR16-105JM
24
1
R7
Res., Chip 4.99k 0.06W 1%
AAC CR05-4991FM
25
1
R8
Res., Chip 93.1k 1/16W 1%
AAC CR05-9312FM
26
1
R9
Res., Chip 2.21k 1/16W 1%
AAC CR05-2211FM
27
1
R14
Res., Chip 470 1/16W 5%
AAC CR05-471JM
28
1
R15
Res., Chip 47k 1/16W 5%
AAC CR05-473JM
29
1
U1
I.C., Voltage Regulator
Linear Technology Corporation LT3724EFE
Additional Demo Board Circuit Components
1
0
C8
Cap., X5R C-4.7µF, 6.3V-0805 6.3V 20%
Taiyo Yuden JMK212BJ475MG-T
2
0
C9
Cap., X5R 1µF 16V 20%
Taiyo Yuden EMK212BJ105MG
3
0
C10
Cap., NPO 220pF 25V 10%
AVX 04023A221KAT2A
4
0
C11
Cap., Aluminum 22µF 35V 10%
Sanyo 35MV22UAX
5
0
D3,D4
Schottky Diode, 40V
Zetex ZHCS400
6
0
L2
Inductor, L-10µH
Murata LQH3C100M24
7
0
R10
Res./Jumper, Chip 0Ω 0.06W 1A
AAC CJ05- 000M
8
0
R11
Res., Chip 107k 0.06W 1%
AAC CR05-1073FM
9
0
R12
Res., Chip 10k 0.06W 5%
AAC CR05-103JM
10
0
R13
Res., Chip 12.4k 1/16W 1%
AAC CR05-1242FM
11
0
U2
I.C., Voltage Regulator
Linear Technology Corporation LT1613CS5
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DEMO MANUAL DC736A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Hardware – For Demo Board Only
1
4
E1, E2, E3, E4
Testpoint, Turret
Mill Max 2501-2
2
0
E5
Testpoint, Turret
Mill Max 2501-2
3
2
JP2, JP1
Headers, 3 Pins 2mm Ctrs.
Comm Con Connectors 2802S-03G2
4
2
XJP1, XJP2
JMP, 3 Pin 1 Row .079CC
Comm Con Connectors CCIJ2MM-138GW
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DEMO MANUAL DC736A
Schematic Diagram
B
A
VCC
1
2
3
C9
1µF
+
4
VIN
CIN1
68µF
GND
63V
100V
CIN3
C12
JP1
0.01µF
R14
470
SHDN
RUN
2.2µF
CIN2
2.2µF
100V
BURST_EN
R6
1M
0603
R7
4.99k
1%
D3
ZHCS400
3
1
R1
1M
0805
2 SHDN
3
R8
93.1k
1%
R15
47k
D5
1N4148WS
L2
5
10µH
1
VIN
SHDN
SW
FB
R3
52.3k
1%
C3
C1
1000pF
100V
R4
VOUT
C8
0805
4.7µF,6.3V
C6
120pF
VC
VFB
402k
1%
C7
1500pF
R9
2.21k
1%
1000pF
10%
U2
LT1613CS5
4
OPTIONAL BOOST BIAS CIRCUIT
(DO NOT INSTALL)
C10
220pF
R11
107k
1%
R12
10k
2
GND
3
3
1
2
3
4
5
6
7
8
NC
NC
SW
TG
BOOST
SHDN
VIN
U1
LT3724EFE
CSS
35V
(Opt)
22µF
C11
D4
ZHCS400
(Opt)
SENSE-
SENSE+
PGND
BURST_EN VCC
VFB
VC
GND
VCC
+
16
15
R2
0 Ohm
14 SW
13
12
C2
10%
0.22µF
C4
D1
BAS19
10%
11
10
0.1µF
9
E5 VBIAS
9V-20V
(Opt)
VIN
VCC
C5
1µF
10%
2
47µH
L1
0.025
1%
0.5W
R5
Q1
Si7852DP
DO5040H-473MLB
COILCRAFT
D2
30BQ060
+
330µF
COUT1
35V
1
VOUT
COUT3
22µF
COUT2
25V
22µF
25V
1
VOUT
GND


STAND-OFF
LTC CONFIDENTIAL - For Customer Use Only

2
E3
VOUT
24V @ 3A
E4
GND
B
A
5
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.
This circuit is proprietary to Linear Technology and supplied
for use with Linear Technology parts.
Customer Notice: Linear Technology has made a best effort to
design a circuit that meets customer-supplied specifications;
however, it remains the customers responsibility to verify proper
and reliable operation in the actual application, Component
substitution and printed circuit board layout may significantly
affect circuit performance or reliability. Contact Linear
Applications Engineering for assistance.
E1
E2
JP2
VIN
30V - 55V
GND
FIXED FREQ.
BURST MODE
VCC
R10
0 Ohm
16V
R13
12.4k
1%
4
Sgnd
17
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DEMO MANUAL DC736A
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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6
Linear Technology Corporation
LT 0912 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2012
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