Linear Technology DC1771A Quick setup guide

dc1771af

DEMO MANUAL DC1771A

DESCRIPTION

LTC3867EUF

Synchronous Buck Converter

with Remote Sensing

Demonstration circuit 1771A is a single output synchro-

nous buck converter featuring the LTC

3867EUF with a

24-lead 4mm ×4mm QFN package.

The DC1771A is configured with a sense resistor. DCR

sensing circuit is optional. Using the inductor’s DCR as

the sense element instead of the on-board sense resistor

saves cost and board space while improving full-load

efficiency over 2%, though the sense resistor provides a

more accurate current limit.

The board has a lot of features including an internal 5V

linear regulator for bias, output voltage remote sense,

programmable nonlinear control to improve load tran-

sient performance, programmable thermal shutdown,

L, LT, LTC, LTM, Burst Mode, 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

optional temperature compensated DCR sense circuit, a

mode selector that allows the converter to run in CCM,

pulse-skippingorBurstMode

operation.Synchronization

to an external clock is also possible.

The input voltage range is from 4.5V to 14V. The LTC3867

data sheet gives a complete description of the part, op-

eration and application information and must be read in

conjunction with this demo manual for DC1771A.

Design files for this circuit board are available at

http://www.linear.com/demo

(TA= 25°C)

PARAMETER CONDITIONS/NOTES VALUE

Input Voltage Range 4.5V ~ 14V

Output Voltage VOUT VIN = 4.5V ~ 14V, IOUT = 0A ~ 15A, JP3: CCM 1.5V ±2% (1.470V ~ 1.530V)

Default Operating Frequency 400kHz

External Clock Sync. Frequency Range 400kHz to 780kHz

Typical Full-Load Efficiency (See Figure 4) VIN = 12V, VOUT = 1.5V, IOUT1 = 15A, fSW = 400kHz 88.3%

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DEMO MANUAL DC1771A

QUICK START PROCEDURE

Figure 1. Test Setup of the DC1771A

Demonstration circuit DC1771A is easy to set up to evalu-

ate the performance of the LTC3867EUF. Please refer to

Figure 1 for proper measurement equipment setup and

follow the procedure below:

1. Place jumpers in the following positions for a typical

application:

JP2 On

JP3 CCM

2. With power off, connect the input power supply, load

and meters as shown in Figure 1. Preset the load to 0A

and VIN supply to 12V.

3. Turn on the power supply at the input.

NOTE: Make surethat the inputvoltage does notexceed 14V.

4. Check the output voltage. The output voltage should

be between 1.470V and 1.530V.

Once the proper output voltage is established, adjust the

load within the operating range and observe the output

voltage regulation, output voltage ripple, efficiency and

other parameters.

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 2 for proper scope

probe technique.

5. Change JP3 jumper position to select different opera-

tion modes. Set jumper to CCM, BURST or P.S. position

toe set forced continuous conduction, burst or pulse-

skipping mode respectively. For synchronizing to an

external clock source, set the jumper to BURST position

and apply the clock signal to MODE/PLLIN turret.

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DEMO MANUAL DC1771A

RAIL TRACKING

Figure 2. Measuring Input or Output Ripple Across Terminals or Directly Across Bulk Capacitor

Figure 3. Measured Efficiency

Demonstration circuit 1771A is configured for an onboard

soft-start circuit. The soft-start ramp rate can be adjusted

by changing the value of C24. Demonstration circuit 1771A

can also be modified to track an external reference. Refer

to Table 1 for tracking options and to the data sheet for

more details.

Table 2. Output Tracking Options

TRK/SS RESISTORS AND CAPACITOR RAIL TRACKING

CONFIGURATION R32 R35 C24 TRK/SS PIN

Soft-Start Without Tracking (Default) 0Ω Open 0.1μF OPEN

VOUT Equals External Ramp 0Ω Open Open External Reference Applied

VOUT Tracking Scaled External Ramp Resistor Divider Open External Reference Applied

LOAD CURRENT (A)

EFFICIENCY (%)

915

10 36 12

CCM

BURST

P. S.

VIN = 12V

VOUT = 1.5V

fSW = 400kHz

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DEMO MANUAL DC1771A

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 2 CIN3, CIN6 CAP, X5R 22μF 20% 25V 1210 TAIYO YUDEN TMK325BJ226MM-T

2 2 COUT1, COUT3 CAP, 330μF 20% 2.5V POSCAP 7343 SANYO 2R5TPE330MF

3 2 COUT4, COUT9 CAP, X5R 100μF 20% 6.3V 1210

4 2 C19, C33 CAP, X5R 1μF 10% 25V 0603 TDK C1608X5R1E105K

5 2 C24, C30 CAP, X7R 1nF 10% 25V 0603 AVX 06033C102KAT

6 1 C25 CAP, X5R 0.1μF 10% 10V 0603 AVX 0603ZD104KAT

7 1 C28 CAP, C0G 100pF 5% 50V 0603 TDK C1608C0G1H101J

8 1 C32 CAP, C0G 10pF 5% 50V 0603 TDK C1608C0G1H100J

9 1 C27 CAP, X5R 4.7μF 10% 10V 0603

10 1 C26 CAP, C0G 470pF 5% 50V 0603 TDK C1608C0G1H471J

11 1 D2 DIODE, CMDSH-3 SOD-323 CENTRAL SEMI CMDSH-3-LTC

12 1 L1 IND., 0.4μH VITEC 59PR9875

13 1 Q1 XSTR, MOSFET LFPAK RENESAS RJK0305DPB

14 1 Q3 XSTR, MOSFET LFPAK RENESAS RJK0329DPB

15 1 RSNSE RES, 0.002Ω 5% 1/4W 2512 PANASONIC ERJM1WTJ2MOU

16 1 U1 IC, LTC3867EUF,QFN 4mm x 4mm

17 4 R32, R36, R56, R58 RES, 0Ω JUMPER 0603 VISHAY CRCW06030000Z0EA

18 2 R9, R10 RES, 100Ω 1%, 1/10W 0603 VISHAY CRCW0603100RFKEA

19 1 R33 RES, 100k 1% 1/10W 0603 VISHAY CRCW0603100KFKEA

20 1 R37 RES, 2.2Ω 5% 1/10W 0603 VISHAY CRCW06032R20JNEA

21 1 R38 RES, 49.9k 1% 1/10W 0603 VISHAY CRCW060349K9FKED

22 1 R39 RES, 75k 1% 1/10W 0603 VISHAY CRCW060375KFKEA

23 1 R40 RES, 10k 1% 1/10W 0603 VISHAY CRCW060310KFKEA

24 1 R51 RES, 37.4KΩ 1% 1/10W 0603 VISHAY CRCW060337K4FKEA

25 6 R49, R50, R53, R57, R59, PTC RES, 10Ω 1% 1/10W 0603 VISHAY CRCW060310R0FKEA

Additional Demo Board Circuit Components

1 1 CIN1 CAP, 150μF 20% 16V SANYO 16SVP150M

2 8 E1, E2, E4-E11 TESTPOINT, TURRET, 0.094" PBF MILL-MAX, 2501-2-00-80-00-00-07-0

3 4 E3, E12-E14 JACK BANANA KEYSTONE, 575-4

Hardware-For Demo Board Only

1 1 JP3 HEADER 4-PIN 0.079 SINGLE ROW SAMTEC, TMM104-02-L-S

2 1 JP2 HEADER 3-PIN 0.079 SINGLE ROW SAMTEC, TMM103-02-L-S

3 2 XJP2, XJP3 SHUNT, 0.079" CENTER SAMTEC, 2SN-BK-G

4 4 (STAND-OFF) STAND-OFF, NYLON 0.50" KEYSTONE, 8832(SNAP ON)

dc1771af

DEMO MANUAL DC1771A

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

dc1771af

DEMO MANUAL DC1771A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ●FAX: (408) 434-0507 ●www.linear.com

LT 0811 • 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 applica-

tion engineer.

Mailing Address:

Linear Technology

1630 McCarthy Blvd.

Milpitas, CA 95035

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