DC2373A - Demo Manual

DEMO MANUAL DC2373A
LT8641
65V, 3.5A Micropower Synchronous
Step-Down Silent Switcher
Description
Demonstration circuit 2373A is a 65V, 3.5A micropower
synchronous step-down Silent Switcher® with spread
spectrum frequency modulation featuring the LT®8641.
The demo board is designed for 5V output from a 5.5V to
65V input. The wide input range allows a variety of input
sources, such as automotive batteries and industrial supplies. The LT8641 is a compact, ultralow emission, high
efficiency, high speed synchronous monolithic step-down
switching regulator that consumes only 2.5μA of quiescent
current when output is regulated at 5V. Top and bottom
power switches, compensation components and other
necessary circuits are inside of the LT8641 to minimize
external components and simplify design.
The SYNC pin on the demo board is grounded by default
for low ripple burst mode operation. Move JP1 to PULSE
SKIPPING position can change the operation mode to
pulse-skipping operation. Once JP1 is on SPREAD SPECTRUM position, VCC is applied to the SYNC pin for low
EMI spread spectrum operation. To synchronous to an
external clock, move JP1 to SYNC and apply the external
clock to the SYNC turret. Figure 1 shows the efficiency of
the circuit at 12V and 24V input in Burst Mode® operation
(input from VIN turret pin). Figure 2 shows the LT8641
temperature rising on DC2373A demo board under different load conditions. The rated maximum load current is
3.5A, while derating is necessary for certain input voltage
and thermal conditions.
The demo board has an EMI filter installed. Under burst
and spread spectrum operation, the EMI performances of
the board (with EMI filter) are shown in Figure 3 and 4. The
red lines in Figure 3 and 4 are CISPR25 Class5 peak limit.
To achieve EMI/EMC performance as shown in Figure 3
and 4, the input EMI filter is required and the input voltage
should be applied at VEMI turret pin.
This board is suitable for a wide range of automotive,
telecom, industrial, and other applications.
The LT8641 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
for DC2373A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2373A
L, LT, LTC, LTM, Linear Technology, Silent Switcher, Burst Mode and the Linear logo are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
Performance Summary
Specifications are at TA = 25°C
SYMBOL
PARAMETER
CONDITIONS
VIN
Input Voltage Range
5.5
VOUT
Output Voltage
4.8
IOUT
Maximum Output Current
fSW
Switching Frequency
EFF
Efficiency
Derating Is Necessary for Certain VIN and
Thermal Conditions
MIN
MAX
65
V
5
5.2
V
3.5
1.85
VIN = 12V, IOUT = 1A
TYP
UNITS
A
2
94
2.15
MHz
%
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DEMO MANUAL DC2373A
Quick Start Procedure
DC2373A is easy to set up to evaluate the performance
of the LT8641. Refer to Figure 5 for proper measurement
equipment setup and follow the procedure below:
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 6 for the proper scope
technique.
1.Set an input power supply that is capable of 65V/3.5A.
Then turn off the supply.
2. With power off, connect the supply to the input terminals
VEMI and GND.
3.Turn on the power at the input.
NOTE: Make sure that the input voltage never exceeds 65V.
4.Check for the proper output voltage of 5V. Turn off the
power at the input.
b. A voltmeter can be placed across the output terminals
in order to get an accurate output voltage measurement.
6.Turn on the power at the input.
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
7.Once the proper output voltage is again established,
adjust the load and/or input within the operating range
and observe the output voltage regulation, ripple voltage, efficiency and other desired parameters.
8.An external clock can be added to the SYNC terminal
when SYNC function is used (JP1 on the SYNC position). Please ensure that the chosen RT sets the LT8641
switching frequency to equal or below the lowest SYNC
frequency. See the data sheet section, Synchronization.
5. Once the proper output voltage is established, connect a
variable load capable of sinking 3.5A at 5V to the output
terminals VOUT and GND. Set the current for 0A.
a. If efficiency measurements are desired, an ammeter
can be put in series with the output load in order to
measure the DC2373A’s output current.
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DEMO MANUAL DC2373A
Quick Start Procedure
100
12V INPUT
95
EFFICIENCY (%)
90
24V INPUT
85
80
75
70
65
60
55
50
0
0.5
1
1.5
2
IOUT (A)
2.5
3
3.5
DC2373a F01
Figure 1. Efficiency vs Load Current at 2MHz Switching Frequency
CASE TEMPERATURE RISE (°C)
60
VIN = 12V, fSW = 1MHz
VIN = 24V, fSW = 1MHz
VIN = 12V, fSW = 2MHz
VIN = 24V, fSW = 2MHz
50
40
30
20
10
0
0
0.5
1
1.5
2.5
2
LOAD CURRENT (A)
3
3.5
DC2373a F02
Figure 2. DC2373A Temperature Rising vs Load Current
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DEMO MANUAL DC2373A
AMPLITUDE (dBµV/m)
Quick Start Procedure
FREQUENCY (MHz)
DC2373a F03
AMPLITUDE (dBµV/m)
Figure 3. LT8641 Demo Circuit EMI Performance in CISPR25 Radiated Emission Test, Antenna Polarization:
Vertical (VIN = 14V, VOUT = 5V, IOUT = 3.5A, 2MHz Switching Frequency)
FREQUENCY (MHz)
DC2373a F04
Figure 4. LT8641 Demo Circuit EMI Performance in CISPR25 Radiated Emission Test, Antenna Polarization:
Horizontal (VIN = 14V, VOUT = 5V, IOUT = 3.5A, 2MHz Switching Frequency)
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DEMO MANUAL DC2373A
Quick Start Procedure
Figure 5. Proper Measurement Equipment Setup
VOUT
GND
Figure 6. Measuring Output Ripple
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DEMO MANUAL DC2373A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
2
C2, C12
CAP, X7R, 0.1µF, 100V, 10%, 0603
MURATA, GRM188R72A104KA35D
2
2
C4, C8
CAP, X7R, 0.1µF, 16V, 10%, 0603
MURATA, GRM188R71C104KA01D
3
1
C5
CAP, C0G, 10pF, 25V, 5%, 0603
AVX, 06033A100CAT2A
4
1
C6
CAP, X5R, 100µF, 10V, 20%, 1210
MURATA, GRM32ER61A107ME20L
5
1
C7
CAP, X7R, 1µF, 25V, 10%, 0603
MURATA, GRM188R71E105KA12D
6
1
C11
CAP, X7S, 4.7µF, 100V, 10%, 1206
AVX, 12061Z475KAT2A
7
1
L1
IND, 2.2µH
VISHAY, IHLP2525CZER2R2M01
8
2
R1, R4
RES, CHIP, 1M, 1/10W, 1%, 0603
VISHAY, CRCW06031M00FKEA
9
1
R2
RES, CHIP, 18.2k, 1/10W, 1%, 0603
VISHAY, CRCW060318K2FKEA
10
1
R3
RES, CHIP, 100k, 1/10W, 1%, 0603
VISHAY, CRCW0603100KFKEA
11
1
R5
RES, CHIP, 191k, 1/10W, 1%, 0603
VISHAY, CRCW0603191KFKEA
12
1
R7
RES, CHIP, 0, 1/10W, 1%, 0604
VISHAY, CRCW06030000Z0EA
13
1
U1
IC, REGULATOR, 20-QFN, UDC
LINEAR TECH,LT8641EUDC#PBF
Additional Demo Board Circuit Components
1
1
C1
CAP, ALUM 22µF, 100V
SUN ELECT, 100CE22BS
2
2
C3, C10
CAP, X7S, 4.7µF, 100V, 10%, 1210
TDK, C3225X7S2A475K200AB
3
1
C9
CAP, X7R, 1µF, 25V, 10%, 0603
MURATA, GRM188R71E105KA12D
4
1
C13
CAP, X7R, 10µF, 10V, 10%, 0805
MURATA, GRM21BR71A106KE51L
5
1
C14
CAP, X7R, 0.1µF, 100V, 10%, 0603
MURATA, GRM188R72A104KA35D
6
1
FB1
FERRITE BEAD, 0805
TDK, MPZ2012S300A
VISHAY, IHLP1212BZERR22M11
7
1
L2
IND, 0.22µH
8
0
R6 (OPT)
RES, 0603
Hardware: For Demo Board Only
1
9
E2 TO E10
TESTPOINT, TURRET, 0.094"
2
1
E1 (OPT)
TESTPOINT, TURRET, 0.094"
3
1
JP1
DOUBLE ROW HEADER 2 x 4 0.079"
MILL-MAX, 2501-2-00-80-00-00-07-0
SULLINS NRPN042PAEN-RC
4
1
XJP1
SHUNT, 0.079" CENTER
SAMTEC 2SN-BK-G
5
4
MH1 TO MH4
STAND-OFF, NYLON 0.50" TALL
KEYSTONE, 8833 (SNAP ON)
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DEMO MANUAL DC2373A
Schematic Diagram
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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 DC2373A
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 0216 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
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●
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