DC2202A - Demo Manual

DEMO MANUAL DC2202A
LT8640
42V, 5A Micropower Synchronous
Step-Down Silent Switcher
Description
Demonstration circuit 2202A is a 42V, 5A micropower
synchronous step-down Silent Switcher® with spread
spectrum frequency modulation featuring the LT®8640.
The demo board is designed for 5V output from a 5.7V
to 42V input. The wide input range allows a variety of
input sources, such as automotive batteries and industrial
supplies. The LT8640 is a compact, ultralow emission,
high efficiency, and high speed synchronous monolithic
step-down switching regulator. The integrated power
switches and inclusion of all necessary circuitry reduce
the components count and solution size. Special Silent
Switcher architecture minimizes EMI/EMC emissions.
Selectable spread spectrum mode can further improve
EMI/EMC performance. Ultralow 2.5μA quiescent current
in Burst Mode® operation achieves high efficiency at very
light loads. Fast minimum on-time of 40ns enables high
VIN to low VOUT conversion at high frequency.
The LT8640 switching frequency can be programmed either
via oscillator resistor or external clock over a 200kHz to
3MHz range. The SYNC pin on the demo board is grounded
(JP1 at BURST position) by default for low ripple Burst
Mode operation. To synchronize to an external clock, move
JP1 to SYNC and apply the external clock to the SYNC turret. Spread spectrum mode and pulse-skipping mode can
be selected respectively by moving JP1 shunt. Figure 1
shows the efficiency of the circuit at 12V and 24V input in
Burst Mode operation (input from VIN turret pin). Figure 2
Performance Summary
SYMBOL
VIN
VOUT
IOUT
PARAMETER
Input Supply Range
Output Voltage
Maximum Output Current
fSW
EFE
Switching Frequency
Efficiency at DC
shows the LT8640 temperature rising on DC2202A demo
board under different load conditions. The rated maximum
load current is 5A, while derating is necessary for certain
input voltage and thermal conditions.
The demo board has an EMI filter installed. The EMI
performance of the board (with EMI filter) is shown on
Figure 3. The red line in Figure 3 is CISPR25 Class 5 peak
limit. The figure shows that the circuit passes the test
with a wide margin. To achieve EMI/EMC performance
as shown in Figure 3, the input EMI filter is required and
the input voltage should be applied at VEMI turret pin. An
inductor L2, which is a 0Ω jumper on the board by default
now, can be added in the EMI filter to further reduce the
conducted emission.
The LT8640 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 demo circuit 2202A. The LT8640 is assembled in a
3mm × 4mm plastic QFN package with exposed pads for
low thermal resistance. Proper board layout is essential
for both low EMI operation and maximum thermal performance. See the data sheet sections Low EMI PCB Layout
and Thermal Considerations and Peak Output Current.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2202A
L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and Silent Switcher are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
Specifications are at TA = 25°C
CONDITIONS
Derating Is Necessary for Certain VIN and
Thermal Conditions
VIN = 12V , IOUT = 3A
MIN
5.7
4.85
5
TYP
1.85
2
93.7
5
MAX
42
5.15
UNITS
V
V
A
2.15
MHz
%
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1
DEMO MANUAL DC2202A
Quick Start Procedure
100
100
VIN = 12V
EFFICIENCY (%)
90
VIN = 24V
85
80
75
70
VOUT = 5V
fSW = 2MHz
SYNC/MODE = GND
65
60
0.5
1
1.5
2 2.5 3 3.5 4
LOAD CURRENT (A)
IOUT = 5A
IOUT = 4.5A
IOUT = 4A
IOUT = 3.5A
90
TEMPERATURE RISING (°C)
95
4.5
80
70
60
50
40
30
VOUT = 5V
fSW = 2MHz
20
10
5
6
12
18
24
30
INPUT VOLTAGE (V)
35
42
DC2202A F02
DC2202A F01
Figure 1. LT8640 Demo Circuit DC2202A Efficiency
vs Load Current (Input from VIN Turret Pin)
Figure 2. LT8640 Demo Circuit DC2202A
Temperature Rising vs Input Voltage
50
VERTICAL POLARIZATION
PEAK DETECTOR
45
AMPLITUDE (dBµV/m)
40
35
30
25
20
15
10
5
CLASS 5 PEAK LIMIT
BURST MODE
SPREAD SPECTRUM MODE
0
–5
0
100
200
300
400
500
600
700
800
900
1000
FREQUENCY (MHz)
50
HORIZONTAL POLARIZATION
PEAK DETECTOR
45
AMPLITUDE (dBµV/m)
40
35
30
25
20
15
10
5
CLASS 5 PEAK LIMIT
BURST MODE
SPREAD SPECTRUM MODE
0
–5
0
100
200
300
400
500
600
700
800
900
1000
FREQUENCY (MHz)
DC2202A DEMO BOARD
(WITH EMI FILTER INSTALLED)
14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz
DC2202A F03
Figure 3. LT8640 Demo Circuit DC2202A EMI Performance in CISPR25
Radiated Emission Test (14V Input from VEMI Turret Pin, IOUT = 4A)
2
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DEMO MANUAL DC2202A
Quick Start Procedure
Demonstration circuit 2202A is easy to set up to evaluate the performance of the LT8640. Refer to Figure 4 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. Measure the input or output voltage
ripple by touching the probe tip directly across the VIN
or VOUT and GND terminals. See Figure 5 for the proper
scope technique.
1.Place JP1 on BURST position.
2.With power off, connect the input power supply to VEMI
and GND. If the EMI/EMC performance is not important,
the input EMI filter can be bypassed by connecting the
input power supply to VIN and GND.
3.With power off, connect the load from VOUT to GND.
4.Turn on the power at the input.
NOTE: Make sure that the input voltage does not exceed
42V.
5.Check for the proper output voltage (VOUT = 5V).
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high or
is shorted.
6.Once the proper output voltage is established, adjust
the load within the operating ranges and observe the
output voltage regulation, ripple voltage, efficiency and
other parameters.
7.An external clock can be added to the SYNC terminal
when SYNC function is used (JP1 on the SYNC position).
Please make sure that RT should be chose to set the
LT8640 switching frequency equal to or below the lowest SYNC frequency. JP1 can also set LT8640 in spread
spectrum mode (JP1 on the SPREAD-SPECTRUM
position) or pulse-skipping mode (JP1 on the PULSESKIPPING position).
Figure 4. Proper Measurement Equipment Setup
VOUT
GND
Figure 5. Measuring Output Ripple
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DEMO MANUAL DC2202A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
2
C2, C12
CAP., X5R, 1µF, 50V, 10% 0603
TDK, C1608X5R1H105K
2
2
C4, C8
CAP., X7R, 0.1µF, 16V, 10% 0603
MURATA, GRM188R71C104KA01D
3
1
C5
CAP., C0G, 10pF, 25V, ±0.25p 0603
AVX, 06033A100CAT2A
4
1
C6
CAP., X5R, 100µF, 10V, 20% 1210
SAMSUNG, CL32A107MPVNNNE
5
2
C7, C9
CAP., X7R, 1.0µF, 25V, 10% 0603
MURATA, GRM188R71E105KA12D
6
1
C11
CAP., X5R, 10µF, 50V, 10% 1206
TDK, C3216X5R1H106K
7
1
C13
CAP., X5R, 4.7µF, 25V, 10% 0603
MURATA, GRM188R61E475KE11D
8
1
L1
INDUCTOR,1.5µH
WÜRTH ELEKTRONIK, 74437346015
8
2
R1, R3
RES., CHIP., 100k, 1/10W, 1% 0603
VISHAY, CRCW0603100KFKEA
9
1
R2
RES., CHIP., 18.2k, 1/10W, 1% 0603
VISHAY, CRCW060318K2FKEA
10
1
R4
RES., CHIP., 1M, 1/10W, 1% 0603
VISHAY, CRCW06031M00FKEA
11
1
R5
RES., CHIP., 243k, 1/10W, 1%, 0603
VISHAY, CRCW0603243KFKEA
12
1
U1
IC, REGULATOR, 20-QFN, UDC
LINEAR TECH. CORP., LT8640EUDC#PBF
Additional Demo Board Circuit Components
1
1
C1
CAP., ALUM 22µF, 63V
SUN ELECT., 63CE22BS
2
2
C3, C10
CAP., X7R, 10µF, 50V, 10% 1210
MURATA, GRM32ER71H106KA12L
3
1
C14
CAP., X7R, 0.1µF, 50V, 10% 0402
TDK, C1005X7R1H104K
4
1
FB1
CHIP BEAD
WÜRTH ELEKTRONIK, 74279226101
5
1
L2
RES., CHIP., 0Ω, 3/4W, 2010
VISHAY, CRCW20100000Z0EF
6
0
R6 (OPT)
RES., 0603
7
1
R7
RES., CHIP., 0, 1/10W, 0603
VISHAY, CRCW06030000Z0EA
Hardware: For Demo Board Only
1
10
E1-E10
TESTPOINT, TURRET, .094" PBF
MILL-MAX, 2501-2-00-80-00-00-07-0
2
1
JP1
2×4, 0.079 DOUBLE ROW HEADER
WÜRTH ELEKTRONIK, 62000821121
3
1
XJP1
SHUNT, 0.079" CENTER
WÜRTH ELEKTRONIK, 60800213421
4
4
MH1-MH4
STAND-OFF, NYLON 0.50" TALL
WÜRTH ELEKTRONIK, 702935000
4
dc2202af
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.
A
B
C
D
E5
E6
E2
E1
SYNC
BURST
VIN
R6
OPT
R1
100K
E10
E7
E9
C14
0.1uF
50V
0402
6
8
5
7
C3
10uF
50V
1210
FB1
74279226101
4
2
3
1
JP1
C10
10uF
50V
1210
5
1. ALL RESISTORS ARE 0603.
ALL CAPACITORS ARE 0603.
NOTES: UNLESS OTHERWISE SPECIFIED
VEMI
TR/SS
GND
PULSE-SKIPPING
SPREAD-SPECTRUM
SYNC
EN/UV
GND
VIN
5.7V - 42V
2010
L2
0
SUNCON
63CE22BS
4
22uF
63V
+ C1
VIN
C7
1uF
25V
C8
0.1uF
C11
10uF
50V
1206
R2
18.2K
(2MHz)
C12
1uF
50V
C2
1uF
50V
15
16
2
17
14
13
**
**
4
CAPACITORS MUST BE PLACED AS CLOSE AS POSSIBLE TO
LT8640.
SHOULD BE PLACED BETWEEN VIN1 AND GND1. C12
** C2
SHOULD BE PLACED BETWEEN VIN2 AND GND2. THESE
TR/SS
INTVCC
SYNC
EN/UV
VIN2
VIN1
RT
3
3
U1
LT8640EUDC
6
7 GND1
10 GND1
11 GND2
GND2
4
GND
18
5
3
FB
PG
BIAS
20
19
1
8
SW 9
SW 21
SW 22
SW
BST
R5
243k
R7
2
C5
R4
0
100k
10pF
1Meg
R3
L1
C4
1.5uH
0.1uF
16V 74437346015
2
C6
100uF
10V
1210
VOUT
C9
1uF
*
1
E8
E4
E3
C13
4.7uF
PG
GND
VOUT
5V / 5A
*
SEE DEMO MANUAL
1
A
B
C
D
DEMO MANUAL DC2202A
Schematic Diagram
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5
DEMO MANUAL DC2202A
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
6
dc2202af
Linear Technology Corporation
LT 0215 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2015
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