Linear Technology DC2530A Demo Manual

DESCRIPTION

DEMO MANUAL DC2530A

LT8640S

42V, 6A Micropower Synchronous

Step-Down Silent Switcher 2

Demonstration circuit 2530A is a 42V, 6A micropower syn­chronous 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 qui­escent current in Burst Mode® operation achieves high
efficiency at very light loads. Fast minimum on-time of
30ns enables high VIN to low V

conversion at high

OUT

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

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

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IN_EMI

V

OUT

I

OUT

f

SW

EFF Efficiency V

Input Supply Range with EMI Filter 5.8 42 V

Output Voltage 4.85 5 5.15 V

Maximum Output Current Derating is Necessary for Certain VIN and Thermal Conditions 6 A

Switching Frequency 1.85 2 2.15 MHz

= 12V, I

IN

Specifications are at TA = 25°C

= 3A 94.3 %

OUT

dc2530af

1

DEMO MANUAL DC2530A

V

OUT

= 5V

POWER LOSS

fSW = 2MHz

SYNC/MODE = GND

EFFICIENCY

VIN = 12V

VIN = 24V

LOAD CURRENT (A)

0.511.522.533.544.555.5

6

60

65

70

75

80

85

90

95

10000.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

EFFICIENCY (%)

POWER LOSS (W)

dc2530 F01

V

OUT

= 5V

fSW = 2MHz

I

OUT

= 6A

I

OUT

= 5A

I

OUT

= 4A

INPUT VOLTAGE (V)

6121824303642

0102030405060708090100

TEMPERATURE RISING (°C)

dc2530 F02

DESCRIPTION

Figure 1. LT8640S Demo Circuit DC2530A Efficiency vs
Load Current (Input from VIN Terminal)

2

Figure 2. LT8640S Demo Circuit DC2530A
Temperature Rising vs Input Voltage

dc2530af

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)

036912151821242730

–40

–30

–20

–10

0

10

20

30

40

50

60

AMPLITUDE (dBµV)

dc2530 F03a

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

05101520

2530354045

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

–5051015202530354045

50

AMPLITUDE (dBµV/m)

dc2530 F03c

DESCRIPTION

DEMO MANUAL DC2530A

Conducted EMI Performance

Radiated EMI Performance

(CISPR25 Radiated Emission Test with Class 5 Peak Limits)

Figure 3. LT8640S Demo Circuit DC2530A EMI Performance (14V input from VEMI, with EMI filter, I

OUT

= 4A)

dc2530af

3

DEMO MANUAL DC2530A

QUICK START PROCEDURE

Demonstration circuit 2530A is easy to set up to evalu­ate 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 (V

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-SPEC­TRUM position) or forced continuous mode (JP1 on
the FCM position).

OUT

= 5V).

-

IN_EMI

4

Figure 4. Proper Measurement Equipment Setup

dc2530af

500ns/DIV

V

OUT

5mV/DIV

AC-COUPLED

dc2530 F06

QUICK START PROCEDURE

V

OUT

C9

GND

Figure 5. Measuring Output Ripple at Output Capacitor C9

DEMO MANUAL DC2530A

Figure 6. LT8640S Demo Circuit DC2530A Output Voltage Ripple
(12V Input, I

= 6A, Full BW)

OUT

dc2530af

5

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

6

dc2530af

SCHEMATIC DIAGRAM

5

4

3

2

1

DEMO MANUAL DC2530A

*

VOUT

5V / 6A

EN

E10

SEE DEMO MANUAL

*

R7

0

C14

OPT

E11

L1

1.5uH

GND

PG

J3

C9

C8

C7

C6

R6

25V

10uF

1uF

10V

100uF

10V

10pF

1M

1210

J4

R4

100K

R3

243K

E12

E7

CLKOUT

E5

1

2

XEL6030-152ME

U1

LT8640S

1

7

SW8SW9SW10SW11SW

BST

OPT

100K

BIAS

EN

17

VIN5VIN6VIN13VIN

14

R8

R1

12

3

GND

16

GND

24

FB

SYNC20VCC

2

23

19

CLKOUT

GND

22

NC

15

NC

4

RT

18

R2

GND
GND
GND
GND

17.8K

28
27
26
25

3

PG

TR/SS

21

C10

50V

10uF

1210

FB1

50V

C11

10uF

C12

0.1uF

C13

0.1uF

J1

VEMI

5.8V - 42V

50V

50V

1210

0402

0402

E2

J2

GND

74279226101

E9

D D

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.

VIN

VIN

C4

0603

1uF

50V

C5

E6

TR/SS

0.1uF

B B

E8

GND

ALL CAPACITORS ARE 0603.

NOTES: UNLESS OTHERWISE SPECIFIED

1. ALL RESISTORS ARE 0603.

A A

C3

1uF

0603

50V

468

50V

C2

10uF

1210

C1

22uF

63V

+

E1

63CE22BS

JP1

1 235

SYNC

E4

BURST

7

FCM

SPREAD-SPECTRUM

SYNC

C C

4

5

dc2530af

7

DEMO MANUAL DC2530A

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

8

dc2530af

LT 0517 • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2017