1
dc1731aabf
DEMO MANUAL
DC1731A-A/DC1731A-B
DESCRIPTION
LTC3646/LTC3646-1
High Efficiency Low Quiescent Current
Step-Down Converter
Demonstration circuit 1731A-A/1731A-B is a step-down
DC/DC converter using LTC3646/LTC3646-1 monolithic
synchronous buck regulator. The input voltage range is
from 4V to 40V. The output voltage range of LTC3646 is
2V to 30V, for LTC3646-1 is 0.6V to 15V. It can deliver up
to 1A of output current. At light load conditions, DC1731A
can operate in Burst Mode
®
operation to improve the ef-
ficiency. The user can choose to use internal or external
compensation. The switching frequency of LTC3646/
LTC3646-1 is programmable from 200kHz to 3MHz. It can
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
be synchronized to an external clock through the MODE/
SYNC pin. The LTC3646/LTC3646-1 data sheet must be
read in conjunction with this demo manual prior to working
on or modifying demonstration circuit 1731A.
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 4V to 40V
Output Voltage VOUT Jumper Selectable 3.3V, 5V
Maximum Continuous Output Current 1A
Default Operating Frequency 1.5MHz
Efficiency VIN = 12V, VOUT = 5V, IOUT = 1A 91.0% See Figure 3
Load Transient VIN = 12V, VOUT = 5V See Figure 4
2
dc1731aabf
DEMO MANUAL
DC1731A-A/DC1731A-B
QUICK START PROCEDURE
Demonstration circuit 1731A is an easy way to evaluate
the performance of the LTC3646/LTC3646-1. 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:
MODE EXTVCC RUN VOUT SELECT
FCC GND ON 3.3V
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 be 0V.
3. Turn on the power at the input. Increase VIN to 12V (Do
not hot-plug the input supply or apply more than the
rated maximum voltage of 40V to the board or the
part may be damaged). The output voltage should be
regulated and deliver the selected output voltage ±2%.
4. Vary the input voltage from 4V to 40V and adjust the
load current from 0A to 1A. Observe the output voltage
regulation, ripple voltage, efficiency, and other param-
eters.
5. To measure input or output ripple, please refer to Figure 2
for proper measurement setup.
Figure 1. Proper Measurement Equipment Setup
VIN
+
+
–
+
–
+
+–
+– LOAD
3
dc1731aabf
DEMO MANUAL
DC1731A-A/DC1731A-B
QUICK START PROCEDURE
Figures 3a and 3b. Measured DC1731A Efficiency at Different VIN and VOUT (Burst Mode Operation Enabled)
LTC3646 Efficiency, VOUT = 3.3V
LTC3646 Efficiency
, VOUT = 5V
Figure 4. Measured Load Transient Responses
LOAD (A)
0
EFFICIENCY (%)
100
10
90
70
50
30
80
60
40
20
0
dc1731aab F03a
1.00.4 0.80.2 0.6
VIN = 5V
VIN = 12V
VIN = 18V
VIN = 24V
VIN = 36V
(a)
LOAD (A)
(b)
0
EFFICIENCY (%)
100
10
90
70
50
30
80
60
40
20
0
dc1731aab F03b
1.00.4 0.80.2 0.6
VIN = 12V
VIN = 18V
VIN = 24V
VIN = 36V
VOUT: 100mV/DIV
IOUT_STEP: 500mA/DIV
dc1731aab F04
VIN = 12V
VO = 5V
0A TO 0.5A LOAD STEP
Figure 2. Measuring VIN or VOUT Ripple
INPUT OR OUTPUT CAPACITOR
4
dc1731aabf
DEMO MANUAL
DC1731A-A/DC1731A-B
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 U1 IC, HIGH EFFICIENCY LOW QUIESCENT CURRENT
STEP-DOWN CONVERTER
LTC3646EDE FOR DC1731A-A LTC3646EDE-1 FOR
DC1731A-B
2 2 CIN2, CIN3 CAP, 1210 10μF 20% 50V X5R TAIYO YUDEN UMK325BJ106MM-T
3 1 COUT1 CAP, 1210 4.7μF 20% 16V X7R TAIYO YUDEN EMK325BJ475MN-T
4 1 COUT2 CAP, 1210 10μF 20% 16V X5R TDK C3225X7R1C106M
5 1 C1 CAP, 0603 4.7μF 10% 10V X5R TDK C1608X5R1A475K-T
6 1 C2 CAP, 0603 0.1μF 10% 50V X7R AVX 06035C104KAT2A
7 1 C3 CAP, 0603 5.6pF 0.25pF 50V NPO AVX 06035A5R6CAT2A
8 1 C5 CAP, 0603 100pF 10% 50V X7R AVX 06035C101KAT2A
9 1 C6 CAP, 0805 2.2μF 20% 50V Y5V TDK C2012Y5V1H225Z
10 2 C7, C9 CAP, 0805 1μF 10% 50V X7R MURATA GRM21BR71H105KA12L
11 1 L1 IND, 4.7μH COILCRAFT XAL5030-472MEB
12 1 R2 RES, 0603 2Ω 5% 1/10W VISHAY CRCW06032R00FNEA
13 1 R3 RES, 0603 100kΩ 5% 1/10W VISHAY CRCW0603100KJNEA
14 1 R7 RES, 0603 60.4kΩ 1% 1/10W VISHAY CRCW060360K4FKED
15 1 R9 RES, 0603 200kΩ 1% 1/10W VISHAY CRCW0603200KFKEA
16 1 R10 RES, 0603 137kΩ 1% 1/10W YAGEO RC0603FR-07137KL
17 1 R11 RES, 0603 84.5kΩ 1% 1/10W VISHAY CRCW060384K5FKEA
18 1 R12 RES, 0603 619kΩ 1% 1/10W VISHAY CRCW0603619KFKEA
Additional Demo Board Circuit Components
1 0 CIN1 CAP, 56μF 20% 50V ALUM. ELEC. OPTION SUN ELEC 50HVH56M OPTION
2 0 C4, C8 CAP, 0603 OPTION OPTION
3 0 D1 DIODE, OPTION OPTION
4 0 R4, R5, R6 RES, 0603 OPTION OPTION
Hardware: For Demo Board Only
1 11 E1-E11 TURRET MILL-MAX 2501-2-00-80-00-00-07-0
2 1 JP1 HEADER, 2mm, 3PIN SAMTEC TMM-103-02-L-S
3 2 JP2, JP5 HEADER, 3PIN, DBL ROW 2mm SAMTEC TMM 103-02-L-D
4 1 JP3 HEADER, 2mm DBL ROW (2X2) 4PIN SAMTEC TMM-102-02-L-D
5 4 MH1, MH2, MH3, MH4 STANDOFF, SNAP ON KEYSTONE_8831
6 4 JP1, JP2, JP3, JP5 SHUNT, 2mm SAMTEC 2SN-BK-G
5
dc1731aabf
DEMO MANUAL
DC1731A-A/DC1731A-B
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
NOTES: UNLESS OTHERWISE SPECIFIED,
1. ALL RESISTOR AND CAPACITOR CASE SIZE ARE 0603.
XAL5030-472MEB
COILCRAFT
[2]
VIN VOUT
[2]
VERSION IC
[3]
OPT
[2]
PG
VIN
SVIN
VOUT
VOUT
EXTVCC
SW
INTVCC
INTVCC
INTVCC
INTVCC
INTVCC
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LTC3646EDE / LTC3646EDE-1
DEMO CIRCUIT 1731A-A/B
CURRENT STEP-DOWN CONVERTER
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LTC3646EDE / LTC3646EDE-1
DEMO CIRCUIT 1731A-A/B
CURRENT STEP-DOWN CONVERTER
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DEMO CIRCUIT 1731A-A/B
CURRENT STEP-DOWN CONVERTER
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
YAN L.PROTO
309/21/12
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
YAN L.PROTO
309/21/12
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
YAN L.PROTO
309/21/12
C2 0.1uFC2 0.1uF
E5
GND
E5
GND
U1
[3]
U1
[3]
BOOST 10
VFB 2
VON 5
PGOOD
6
PGND
15
SW 9
SVIN 14
EXTVCC 12
ITH
3
PVIN 8
RT
4
INTVCC 11
MODE/SYNC
7
RUN
13
SGND
1
CIN2
10uF
50V
1210
CIN2
10uF
50V
1210
R12
619k
1%
R12
619k
1%
E11
GND
E11
GND
R4
OPT
R4
OPT
C6
2.2uF 50V
0805
C6
2.2uF 50V
0805
L1 4.7uHL1 4.7uH
E2
VIN
E2
VIN
R5
OPT
R5
OPT
R3
100k
R3
100k
C5
100pF
C5
100pF
JP2
MODE / SYNC
FCC
BURST
SYNC
JP2
MODE / SYNC
FCC
BURST
SYNC
1 2
3 4
5 6
JP5
EXTVCC
EXTVCC
VOUT
GND
JP5
EXTVCC
EXTVCC
VOUT
GND
1 2
3 4
5 6
JP1
ON
OFF
RUN
JP1
ON
OFF
RUN
1
3
2
CIN3
10uF
50V
1210
CIN3
10uF
50V
1210
E6
INTVCC
E6
INTVCC
+
CIN1
OPT
+
CIN1
OPT
E7
GND
E7
GND
D1
DFLS1200
D1
DFLS1200
E10
SYNC
E10
SYNC
C1
4.7uF
C1
4.7uF
C3
5.6pF
C3
5.6pF
E8
EXTVCC
E8
EXTVCC
E4
VOUT
E4
VOUT
C9
1uF
0805
C9
1uF
0805
C7
1uF
0805
C7
1uF
0805
10uF
COUT2
1210
16V
10uF
COUT2
1210
16V
C4
OPT
C4
OPT
C8
OPT
C8
OPT
R11
84.5k
1%
R11
84.5k
1%
4.7uF
COUT1
1210
16V
4.7uF
COUT1
1210
16V
R9
200k
1%
R9
200k
1%
R6
OPT
R6
OPT
R7
60.4k
1%
R7
60.4k
1%
E3
GND
E3
GND
R2
2
R2
2
E1
SVIN
E1
SVIN
E9
PGOOD
E9
PGOOD
JP3
VOUT SELECT
3.3V
5V
JP3
VOUT SELECT
3.3V
5V
1 2
3 4
R10
137k
1%
R10
137k
1%
6
dc1731aabf
DEMO MANUAL
DC1731A-A/DC1731A-B
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2012
LT 1112 • 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
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Copyright © 2004, Linear Technology Corporation