Analog Devices Linear Technology 2658A Quick setup guide

dc2658af

DEMO MANUAL DC2658A

Description

LT8643S

42V, 6A Synchronous

Step-Down Silent Switcher 2

Demonstration circuit 2658A is a 42V, 6A synchronous

step-down second generation SILENT SWITCHER with

spread spectrum frequency modulation featuring the

8643S. 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 LT8643S 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/EMCemissions by reducing

layout sensitivity. Selectable spread spectrum mode can

further improve EMI/EMC performance. Fast minimum

on-time of 30ns enables high VIN to low VOUT conversion

at high frequency.

The LT8643S switching frequency can be programmed

either via oscillator resistor or external clock over a

200kHz to 3MHz range. The default frequency of demo

circuit 2658A 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 and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

performance summary

the LT8643S temperature rising on DC2658A 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 perfor-

mance of the board (with EMI filter) is shown on Figure 3.

Thered linein RadiatedEMI Performance isCISPR25 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 VIN_EMI 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 LT8643S 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 DC2658A. The LT8643S 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/DC2658A

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 94.2 %

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dc2658af

DEMO MANUAL DC2658A

POWER LOSS

= 2MHz

SYNC/MODE = GND

OUT

= 5V

EFFICIENCY

= 12V

= 24V

LOAD CURRENT (A)

0.5

1.5

2.5

3.5

4.5

5.5

100

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

EFFICIENCY (%)

POWER LOSS (W)

DC2658A F01

= 2MHz

OUT

= 6A

OUT

= 5A

OUT

= 4A

OUT

= 5V

INPUT VOLTAGE (V)

100

CASE TEMPERATURE RISING (°C)

DC2658A F02

Figure 1. LT8643S DC2658A Efficiency

vs Load Current (Input from VIN Terminal)

Figure 2. LT8643S DC2658A Case

Temperature Rising vs Input Voltage

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dc2658af

DEMO MANUAL DC2658A

Radiated EMI Performance

(CISPR25 Radiated Emission Test with Class 5 Peak Limits)

Conducted EMI Performance

(WITH EMI FILTER INSTALLED)

14V INPUT TO 5V OUTPUT AT 4A, f

= 2MHz

SPREAD SPECTRUM MODE

FIXED FREQUENCY MODE

FREQUENCY (MHz)

–40

–30

–20

–10

AMPLITUDE (dBµV)

DC2658 F03a

VERTICAL POLARIZATION

PEAK DETECTOR

CLASS 5 PEAK LIMIT

SPREAD SPECTRUM MODE

FIXED FREQUENCY MODE

FREQUENCY (MHz)

100

200

300

400

500

600

700

800

900

1000

–5

AMPLITUDE (dBµV/m)

DC2658 F03b

(WITH EMI FILTER INSTALLED)

14V INPUT TO 5V OUTPUT AT 4A, f

= 2MHz

HORIZONTAL POLARIZATION

PEAK DETECTOR

CLASS 5 PEAK LIMIT

SPREAD SPECTRUM MODE

FIXED FREQUENCY MODE

FREQUENCY (MHz)

100

200

300

400

500

600

700

800

900

1000

–5

AMPLITUDE (dBµV/m)

DC2658 F03c

Figure 3. LT8643S Demo Circuit DC2658A EMI Performance

(14V Input from VIN_EMI, with EMI Filter, IOUT = 4A)

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dc2658af

DEMO MANUAL DC2658A

Quick start proceDure

Demonstration circuit 2658A is easy to set up to evalu-

ate the performance of the LT8643S. 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

VIN_EMI 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 LT8643S switching frequency equal to or below the

lowest SYNC frequency. JP1 can also set LT8643S in

spread spectrum mode (JP1 on the SPREAD-SPEC-

TRUM position) or forced continuous mode (JP1 on

the FCM position).

POWER

SUPPLY

IIN IOUT

VOUT

VIN_EMI

–

LOAD

–

+–

–

Figure 4. Proper Measurement Equipment Setup

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dc2658af

DEMO MANUAL DC2658A

Quick start proceDure

DC2658A F06

500ns/DIV

VOUT

5mV/DIV

AC-COUPLED

Figure 5. Measuring Output Ripple at Output Capacitor C9

Figure 6. LT8643S Demo Circuit DC2658A Output Voltage Ripple

(12V Input, IOUT = 6A, Full BW)

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dc2658af

DEMO MANUAL DC2658A

parts List

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 2 C2, C12 CAP., X5R, 1μF, 50V, 10%, 0603 MURATA, GRM188R61H105KAALD

2 1 C5 CAP., C0G, 330pF, 50V, 5%, 0603 MURATA, GRM1885C1H331JA01D

3 1 C6 CAP., X5R, 100μF, 10V, 20% 1210 MURATA, GRM32ER61A107ME20L

4 1 C8 CAP., X7R, 0.1μF, 16V, 10%, 0603 MURATA, GRM188R71C104KA01D

5 1 C9 CAP., X5R, 22μF, 10V, 20%, 0603 SAMSUNG, CL10A226MPMNUBE

6 1 C16 CAP., C0G, 4.7pF, 50V, ±0.1pF, 0603 MURATA, GRM1885C1H4R7BA01D

7 1 C17 CAP., X7R, 10μF, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12L

8 1 C20 CAP., X7R, 1μF, 10V, 10%, 0603 MURATA, GRM188R71A105KA61D

9 1 L1 INDUCTOR,1.5μH COILCRAFT, XEL6030-152ME

10 2 R1, R5 RES., CHIP, 100k, 1/10W, 1% 0603 VISHAY, CRCW0603100KFKEA

11 1 R2 RES., CHIP, 17.8k, 1/10W, 1% 0603 VISHAY, CRCW060317K8FKEA

12 1 R3 RES., CHIP, 243k, 1/10W, 1%, 0603 VISHAY, CRCW0603243KFKEA

13 1 R4 RES., CHIP, 8.45k, 1/10W, 1%, 0603 VISHAY, CRCW06038K45FKEA

14 1 R7 RES., CHIP, 1M, 1/10W, 1%, 0603 VISHAY, CRCW06031M00FKEA

15 1 U1 I.C., STEP-DOWN SWITCHER, 4mm × 4mm LQFN LINEAR TECH., LT8643SEV#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 2 C14, C21 CAP., X7R, 0.1μF, 50V, 10%, 0402 MURATA, GRM155R71H104KE14D

4 0 C15, C18 (OPT) CAP., OPTION, 0603

5 1 FB1 BEAD, FERRITE, 100Ω, 1812 WURTH ELEKTRONIK, 74279226101

6 0 R6 (OPT) RES., OPTION, 0603

7 1 R8 RES., CHIP, 0Ω, 1/10W, 1%, 0603 VISHAY, CRCW06030000Z0EA

Hardware: For Demo Board Only

1 8 E1, E5-E9, E11, E14 TESTPOINT, TURRET, .094" MILL-MAX, 2501-2-00-80-00-00-07-0

2 4 E2, E10, E12, E13 TESTPOINT, TURRET, .064" MILL-MAX, 2308-2-00-80-00-00-07-0

3 1 JP1 2×4, 0.079 DOUBLE ROW HEADER WURTH ELEKTRONIK, 62000821121

4 1 XJP1 SHUNT, .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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dc2658af

DEMO MANUAL DC2658A

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

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

17.8K

C17

10uF

50V

1210

E11 EN

FB1

74279226101

GND

C21

0.1uF

0402

50V R8

GND

1uF

50V

OPT

JP1

1 2

C14

0.1uF

0402

50V

E8 PG

SYNC

243K

22uF

63V

63CE22BS C6

100uF

10V

1210

C12

1uF

50V

330pF

10uF

1210

50V

TR/SS

VOUT

5V / 6A

C20

1uF

10V

VIN

5.8V - 42V

C16

4.7pF

J4 GND

C10

10uF

1210

50V

E10

VIN_EMI

C15

OPT

0.1uF

22uF

10V

XEL6030

1.5uH

C18

OPT

100K

E6 CLKOUT

E12

LT8643SEV

SYNC

VCC

BIAS

BST

GND

TR/SS

GND

VIN

CLKOUT

GND

100K

8.45K

E13

E14

VIN

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dc2658af

DEMO MANUAL DC2658A

LT 0817 • 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.

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

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