Linear Technology DC2530A Quick setup guide

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DEMO MANUAL DC2530A
DESCRIPTION
LT8640S
42V, 6A Micropower Synchronous
Step-Down Silent Switcher 2
Demonstration circuit 2530A is a 42V, 6A micropower syn-
chronous step-down second generation Silent Switcher
®
with spread spectrum frequency modulation featuring
the LT8640S. The demo board is designed for 5V output
from a 5.8V to 42V input. The wide input range allows a
variety of input sources, such as automotive batteries and
industrial supplies. The LT8640S is a compact, ultralow
emission, high efficiency, and high speed synchronous
monolithic step-down switching regulator. The integrated
bypass capacitors optimize all the fast current loops and
make it easier to minimize EMI/EMC emissions by reduc-
ing layout sensitivity. Selectable spread spectrum mode
can further improve EMI/EMC performance. Ultralow qui-
escent current in Burst Mode
®
operation achieves high
efficiency at very light loads. Fast minimum on-time of
30ns enables high V
IN
to low V
OUT
conversion at high
frequency.
The LT8640S switching frequency can be programmed
either via oscillator resistor or external clock over a
200kHz to 3MHz range. The default frequency of demo
circuit 2530A is 2MHz. 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 terminal. Spread spectrum mode and forced
continuous mode can be selected respectively by moving
JP1 shunt. Figure 1 shows the efficiency of the circuit at
12V input and 24V input in Burst Mode Operation (input
from VIN terminal to bypass the EMI filter). Figure 2 shows
L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and Silent Switcher are
registered trademarks of Analog Devices, Inc. All other trademarks are the property of their
respective owners.
PERFORMANCE SUMMARY
the LT8640S temperature rising on DC2530A demo board
under different load conditions. The rated maximum load
current is 6A, 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 Radiated EMI Performance 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 terminal. An inductor can be added in the EMI
filter to further reduce the conducted emission. The EMI
filter can be bypassed by applying the input voltage at
VIN terminal.
The LT8640S 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 2530A. The LT8640S is assembled in a
4mm × 4mm LQFN package with exposed pads for low
thermal resistance. The layout recommendations for low
EMI operation and maximum thermal performance are
available in the data sheet section 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/DC2530A
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN_EMI Input Supply Range with EMI Filter 5.8 42 V
VOUT Output Voltage 4.85 5 5.15 V
IOUT Maximum Output Current Derating is Necessary for Certain VIN and Thermal Conditions 6 A
fSW Switching Frequency 1.85 2 2.15 MHz
EFF Efficiency VIN = 12V, IOUT = 3A 94.3 %

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DEMO MANUAL DC2530A
DESCRIPTION
Figure 1. LT8640S Demo Circuit DC2530A Efficiency vs
Load Current (Input from VIN Terminal)
Figure 2. LT8640S Demo Circuit DC2530A
Temperature Rising vs Input Voltage
V
OUT
= 5V
POWER LOSS
f
SW
= 2MHz
SYNC/MODE = GND
EFFICIENCY
V
IN
= 12V
V
IN
= 24V
LOAD CURRENT (A)
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
60
65
70
75
80
85
90
95
100
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
EFFICIENCY (%)
POWER LOSS (W)
dc2530 F01
V
OUT
= 5V
f
SW
= 2MHz
I
OUT
= 6A
I
OUT
= 5A
I
OUT
= 4A
INPUT VOLTAGE (V)
6
12
18
24
30
36
42
0
10
20
30
40
50
60
70
80
90
100
TEMPERATURE RISING (°C)
dc2530 F02

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DEMO MANUAL DC2530A
DC2530A DEMO BOARD
(WITH EMI FILTER INSTALLED)
14V INPUT TO 5V OUTPUT AT 4A, f
SW
= 2MHz
SPREAD SPECTRUM MODE
FIXED FREQUENCY MODE
FREQUENCY (MHz)
0
3
6
9
12
15
18
21
24
27
30
–40
–30
–20
–10
0
10
20
30
40
50
60
AMPLITUDE (dBµV)
dc2530 F03a
Conducted EMI Performance
Radiated EMI Performance
(CISPR25 Radiated Emission Test with Class 5 Peak Limits)
VERTICAL POLARIZATION
PEAK DETECTOR
CLASS 5 PEAK LIMIT
SPREAD SPECTRUM MODE
FIXED FREQUENCY MODE
FREQUENCY (MHz)
0
100
200
300
400
500
600
700
800
900
1000
–5
0
5
10
15
20
25
30
35
40
45
50
AMPLITUDE (dBµV/m)
dc2530 F03b
DC2530A DEMO BOARD
(WITH EMI FILTER INSTALLED)
14V INPUT TO 5V OUTPUT AT 4A, f
SW
= 2MHz
HORIZONTAL POLARIZATION
PEAK DETECTOR
CLASS 5 PEAK LIMIT
SPREAD SPECTRUM MODE
FIXED FREQUENCY MODE
FREQUENCY (MHz)
0
100
200
300
400
500
600
700
800
900
1000
–5
0
5
10
15
20
25
30
35
40
45
50
AMPLITUDE (dBµV/m)
dc2530 F03c
Figure 3. LT8640S Demo Circuit DC2530A EMI Performance (14V input from VEMI, with EMI filter, IOUT = 4A)
DESCRIPTION

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DEMO MANUAL DC2530A
IN_EMI
QUICK START PROCEDURE
Demonstration circuit 2530A is easy to set up to evalu-
ate the performance of the LT8640S. 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 output voltage ripple by
touching the probe tip directly across the output capaci-
tor. See Figure 5 for the proper scope technique. Figure 6
shows the output voltage ripple measured at the output
capacitor C9.
1. Place JP1 on BURST position.
2. With power off, connect the input power supply to
VEMI and GND. If the input EMI filter is not desired,
connect 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 posi-
tion). Please make sure that R2 should be chose to set
the LT8640S switching frequency equal to or below the
lowest SYNC frequency. JP1 can also set LT8640S in
spread spectrum mode (JP1 on the SPREAD-SPEC-
TRUM position) or forced continuous mode (JP1 on
the FCM position).
Figure 4. Proper Measurement Equipment Setup

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DEMO MANUAL DC2530A
500ns/DIV
V
OUT
5mV/DIV
AC-COUPLED
dc2530 F06
QUICK START PROCEDURE
Figure 5. Measuring Output Ripple at Output Capacitor C9
Figure 6. LT8640S Demo Circuit DC2530A Output Voltage Ripple
(12V Input, IOUT = 6A, Full BW)
VOUT
GND
C9

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DEMO MANUAL DC2530A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C2 CAP., X7R, 10μF, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12L
2 2 C3, C4 CAP., X5R, 1μF, 50V, 10%, 0603 MURATA, GRM188R61H105KAALD
3 1 C5 CAP., X7R, 0.1μF, 16V, 10%, 0603 MURATA, GRM188R71C104KA01D
4 1 C6 CAP., NP0, 10pF, 50V, 5%, 0603 MURATA, GRM1885C1H100JA01D
5 1 C7 CAP., X5R, 100μF, 10V, 20% 1210 MURATA, GRM32ER61A107ME20L
6 1 C8 CAP., X7R, 1μF, 10V, 10%, 0603 MURATA, GRM188R71A105KA61D
7 1 C9 CAP., X5R, 10μF, 25V, 20%, 0603 MURATA, GRM188R61E106MA73D
8 1 L1 INDUCTOR, 1.5μH COILCRAFT, XEL6030-152ME
9 2 R1, R4 RES., CHIP, 100k, 1/10W, 1% 0603 VISHAY, CRCW0603100KFKEA
10 1 R2 RES., CHIP, 17.8k, 1/10W, 1% 0603 VISHAY, CRCW060317K8FKEA
11 1 R3 RES., CHIP, 243k, 1/10W, 1%, 0603 VISHAY, CRCW0603243KFKEA
12 1 R6 RES., CHIP, 1M, 1/10W, 1%, 0603 VISHAY, CRCW06031M00FKEA
13 1 U1 I.C., STEP-DOWN SWITCHER, 4MMx4MM LQFN LINEAR TECH., LT8640SEV#PBF
Additional Demo Board Circuit Components
1 1 C1 CAP., ALUM 22μF, 63V SUN ELECT., 63CE22BS
2 2 C10, C11 CAP., X7R, 10μF, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12L
3 2 C12, C13 CAP., X7R, 0.1μF, 50V, 10%, 0402 MURATA, GRM155R71H104KE14D
4 0 C14 (OPT) CAP., OPTION, 0603
5 1 FB1 BEAD, FERRITE, 100Ω, 1812 WURTH ELEKTRONIK, 74279226101
6 1 R7 RES., CHIP, 0Ω, 1/10W, 1%, 0603 VISHAY, CRCW06030000Z0EA
7 0 R8 (OPT) RES., OPTION, 0603
Hardware: For Demo Board Only
1 7 E1, E4-E8, E10 TESTPOINT, TURRET, 0.094" MILL-MAX, 2501-2-00-80-00-00-07-0
2 4 E2, E9, E11, E12 TESTPOINT, TURRET, 0.061" MILL-MAX, 2308-2-00-80-00-00-07-0
3 1 JP1 2X4, 0.079 DOUBLE ROW HEADER WURTH ELEKTRONIK, 62000821121
4 1 XJP1 SHUNT, 0.079" CENTER WURTH ELEKTRONIK, 60800213421
5 4 J1-J4 JACK BANANA KEYSTONE, 575-4
6 4 MH1-MH4 STAND-OFF, NYLON 0.50" TALL WURTH ELEKTRONIK, 702935000

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DEMO MANUAL DC2530A
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM
5
5
4
4
3
3
2
2
1
1
D D C C B B A A
ALL CAPACITORS ARE 0603.
NOTES: UNLESS OTHERWISE SPECIFIED 1. ALL RESISTORS ARE 0603.
SYNC
BURST
SPREAD-SPECTRUM
FCM
SEE DEMO MANUAL
*
*
R2
17.8K
C2 10uF
50V
1210
E10 EN
C12 0.1uF 0402 50V
FB1
74279226101
E8
GND
R7
0
E2
GND
C4
1uF 50V
0603
R8
OPT
JP1
1 2 3 5 7
4 6 8
R3
243K
E7 PG
E4
SYNC
R6
1M
+
C1 22uF 63V 63CE22BS C7
100uF 10V 1210
J1
5.8V - 42V
C3 1uF
50V
0603
C10
10uF 1210
50V
E6
TR/SS
J3
VOUT
5V / 6A
C8 1uF
10V
E1
VIN
C6 10pF
J4 GND
E9
VEMI
C5 0.1uF
C13 0.1uF 0402 50V
C9
10uF
25V
L1
1.5uH
XEL6030-152ME
C11
10uF 1210
50V
C14 OPT
J2
R4
100K
E5 CLKOUT
E11
U1 LT8640S
EN
17
SYNC
20
VCC
2
RT
18
FB
24
PG
23
BIAS
1
BST
7
GND
3
TR/SS
21
GND
16
VIN
5
VIN
6
VIN
13
VIN
14
GND
22
CLKOUT
19
SW
8
SW
9
SW
10
SW
11
SW
12
NC
4
NC
15
GND
25
GND
26
GND
27
GND
28
R1
100K
E12
VIN

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DEMO MANUAL DC2530A
 LINEAR TECHNOLOGY CORPORATION 2017
LT 0517 • PRINTED IN USA
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.
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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.).
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customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
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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.
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