Linear Technology DC1928A Quick setup guide
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DEMO MANUAL DC1928A
DESCRIPTION
LTC3867EUF
High Efficiency Synchronous
Buck Converter
Demonstrationcircuit1928Ais asingleoutputsynchronous
buck converter featuring the LT C
®
3867EUF in a 24-lead
4mm x 4mm QFN package.
The DC1928A is configured with a sense resistor. Inductor
DCR sensing circuit is optional. Using the inductor’s DCR
as the sense element instead of the onboard sense resistor
saves cost, board space while improving efficiency. Using
a sense resistor provides 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, an
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode 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,
and selectable continuous, pulse-skipping or Burst Mode
®
operation. Synchronization to an external clock is also
possible.
The input voltage range is from 18V to 36V. The LTC3867
data sheet gives a complete description of the part, opera-
tion and application information and must be read in con-
junction with this demo manual for DC1928A.
Design files for this circuit board are available at
http://www.linear.com/demo
Specifications are at TA= 25°C
PARAMETER CONDITIONS / NOTES VALUE
Input Voltage Range 18V ~ 36V
Output Voltage, VOUT VIN = 18V ~ 36V, IOUT = 0A ~ 12A, JP3: CCM 12V ±2% (11.76V ~ 12.24V)
Default Operating Frequency (Typical) 250kHz
External Clock Sync. Frequency Range 200kHz to 780kHz
Typical Full Load Efficiency (See Figure 3) VIN = 24V, VOUT = 12V, IOUT1 = 12A, fSW = 250kHz 97.6%
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DEMO MANUAL DC1928A
QUICK START PROCEDURE
Demonstration circuit DC1928A is easy to set up to evalu-
ate the performance of the LTC3867EUF. Please refer to
Figure 2 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 24V.
3. Turn on the power supply at the input.
Note:Makesure that theinput voltage doesnot exceed 36V.
4. Check the output voltage. The output voltage should
be between 11.76V and 12.24V.
Oncethe proper output voltage isestablished, 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. ChangeJP3 jumper position to selectdifferent operation
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.
Figure 1. Test Setup of DC1928A
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DEMO MANUAL DC1928A
QUICK START PROCEDURE
RAIL TRACKING
Figure 2. Measuring Input or Output Ripple Across Terminals or Directly Across Bulk Capacitor
ILOAD (A)
10
EFFICIENCY (%)
80
70
60 5 9
37 11
26 10
48 12
90
100
75
65
85
95
PULSE-SKIPPING
FCM
BURST
Figure 3. Measured Efficiency
Demonstration circuit 1928A is configured for an onboard
soft-start circuit. The soft-start ramp rate can be adjusted
by changingthe value of C24. Demonstration circuit1928A
can also be modified to track an external reference. Refer
to Table 1 for tracking options and to the data sheet for
more details.
CONFIGURATION
TRK/SS RESISTORS AND CAPACITOR RAIL TRACKING
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
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DEMO MANUAL DC1928A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 CIN1 CAP, ALUM, 56µF 20% 50V SUN ELECT 50HVH56M
2 2 CIN3, CIN6 CAP, X5R 10µF 20% 50V 1210 TAIYO YUDEN UMK325BJ106MM-T
5 2 COUT1, COUT2 CAP, POSCAP 150µF 20% 16V 7343 SANYO, 16TQC150MYF
7 2 COUT4, COUT8 CAP, X5R 22µF 20% 16V 1210 AVX 1210YD226MAT2A
9 1 C32 CAP., X7R 10pF 10% 25V 0603 AVX 06033C100KAT2A
10 1 C33 CAP, X5R 1µF 10% 50V 0603 TDK C1608X5R1E105K
11 1 C19 CAP, X5R 0.033µF 10% 50V 0603 AVX 06035D333KAT2A
12 1 C30 CAP, X7R 1nF 10% 25V 0603 AVX 06033C102KAT
13 2 C24, C25 CAP, X5R 0.1µF 10% 10V 0603 AVX 0603ZD104KAT
14 1 C26 CAP, C0G 470pF 5% 50V 0603 MURATA GCM1885C1H471JA16D
15 1 C27 CAP, X5R 4.7µF 10% 10V 0603 AVX 0603ZD475KAT2A
16 1 C28 CAP, C0G 100pF 5% 50V 0603 TDK C1608COG1H101JK
17 1 D1 DIODE, 6.8V SOD-323 CENTRAL CMDZ6L8
18 1 D2 DIODE, SOD-323 CENTRAL SEMI CMDSH05-4-LT C
23 1 L1 IND., 7µH WURTH., 7443630700
24 2 Q1, Q3 XSTR, MOSFET LFPAK INFINEON BSC035N04LSG
28 1 RSNSE RES, 3mΩ 1% 1W 2512 PANASONIC ERJM1WTF3M0U
29 2 R9, R10 RES, 100Ω 1% 1/10W 0603 NIC NRC06F1000TRF
31 4 R32, R36, R56, R58 RES, 0Ω 1/10W 0603 VISHAY CRCW06030000Z0EA
32 1 R33 RES, 100k 1% 1/10W 0603 NIC NRC06F1003TRF
33 1 R37 RES, 2.2Ω 5% 1/10W 0603 NIC NRC06F2R20TRF
34 1 R39 RES, 191KΩ 1% 0603 VISHAY CRCW060375K0FKEA
35 4 R38, R53, R57, R59 RES, 10k 1% 0603 NIC NRC06F1002TRF
36 1 R40 RES, 44.2k 1% 0603 VISHAY CRCW060344K2FKEA
37 1 R51 RES, 30.1k 1% 0603 NIC NRC06f3012TRF
38 3 R49, R50, PTC RES, 10Ω 1% 0603 NIC NRC06f10R0TRF
39 1 U1 IC., LTC3867EUF, QFN 4mm x 4mm LINEAR TECH. LTC3867EUH#PBF
Additional Demo Board Circuit Components
1 2 COUT5, COUT7 (OPT)
2 3 CIN4, CIN5, CIN7, CAP, X5R 22µF 20% 25V 1210
3 1 COUT3 (OPT) CAP, POSCAP 7343
4 3 C18, C23, C29 (OPT) CAP, 0603
5 2 Q2, Q4 (OPT) XSTR, MOSFET LFPAK
6 1 Q5 (OPT) XSTR, MOSFET, DUAL N-CHANNEL
7 13 R1, R27, R29, R35, R42, R43,
R46-R48, R52, R54, R55, RNTC (OPT)
RES, 0603
Hardware-For Demo Board Only
1 8 E1, E2, E4-E11 TURRET, 0.094" MILL-MAX 2501-2-00-80-00-00-07-0
2 1 JP2 HEADER, 3-PIN SAMTEC TMM-103-02-L-S
3 1 JP3 HEADER, 4-PIN SAMTEC TMM-104-02-L-S
4 4 J1-J4 JACK, BANANA KEYSTONE 575-4
5 2 XJP2, XJP3 SHUNT SAMTEC 2SN-BK-G
6 4 STANDOFF, SNAP ON KEYSTONE 8832
7 1 FAB, PRINTED CIRCUIT BOARD DEMO CIRCUIT 1928A
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DEMO MANUAL DC1928A
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
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DEMO MANUAL DC1928A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ●FAX: (408) 434-0507 ●www.linear.com
LINEAR TECHNOLOGY CORPORATION 2013
LT 0513 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LT C ) 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 LT C 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 LT C 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. LT C assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LT C 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 LT C applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
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