Linear Technology LT3759 Quick setup guide

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dc1787af
DEMO MANUAL DC1787A
DESCRIPTION
LT3759
Wide Input Voltage Range
Boost/SEPIC/Inverting Controller
Demonstration circuit 1787A is a wide input voltage
range SEPIC converter featuring the LT3759 controller. It
converts a 2.8V~36V input to a 12V output, with 1A load
current capability for VIN ≥ 4V. The converter operates at
a 300 kHz nominal switching frequency, with 91% peak
efficiency. The DC1787A can be easily modified to gener-
ate other output voltages, and can also be optimized for
efficiency and size with narrower input voltage ranges.
The LT3759 is a boost/SEPIC/Inverting controller with a
wide input voltage range, suitable for applications from
single-cell lithium-ion battery portable electronics to high
voltage automotive and industrial power supplies. It also
exhibits low shutdown quiescent current of 1A, making it
an ideal fit for battery-operated systems. Thanks to a novel 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
FBX pin architecture, the LT3759 can be connected directly
to a divider from either positive output or negative output
voltage to ground. It also packs many popular features
such as soft-start, input undervoltage lockout, adjustable
frequency and synchronization in a small 12-lead exposed
pad MSOP package.
The LT3759 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 1787A.
Design files for this circuit board are available at
http://www.linear.com/demo
(TA= 25°C)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage Range, VIN 2.8 12 36 V
Minimum Startup Voltage 3.0 V
Switching Frequency IOUT = 0.5A 300 kHz
Output Voltage, VOUT V
IN = 2.8V~36V
IOUT = 0mA~0.5A
11.64 12.0 12.36 V
Maximum Continuous Output Current, IOUT VIN ≥ 2.8V 0.5 A
VIN ≥ 4.0V 1 A
Output Voltage Ripple (Peak-to-Peak) VIN = 12V, IOUT = 1A 90 mV
Typical Efficiency VIN = 12V, IOUT = 1A 91 %

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DEMO MANUAL DC1787A
QUICK START PROCEDURE
Demo circuit 1787A is easy to set up to evaluate the
performance of the LT3759. Refer to Figure 1 for proper
measurement equipment setup and follow the procedure.
1. With power off, connect the input power supply to the
VIN (E1) and GND (E2) terminals on the demo circuit.
NOTE: Minimize the voltage drop and transient on the
input wires between the power supply and input terminals
of the demo circuit.
2. Connect load to the VOUT (E6) and GND (E5) terminals
on the demo circuit. Connect voltage and current meters
as shown in Figure 1. Preset the load to 0.5A or less,
and VIN supply to be 0V.
3. Place jumpers in the following positions for a typical
12V application:
EN (JP1) SYNC (JP2)
ON OFF
NOTE: The demo circuit configures the shutdown voltage
at typical 2.5V, which means that the input voltage can be
dropped to as low as 2.5V, once it starts up. The startup
voltage is 3.0V but can be adjusted by changing R1 and
R3 values.
5. Check for the proper output voltages. The output should
be regulated at 12V (±3%).
NOTE: If there is no output, or output is out of spec, tem-
porarily disconnect the load from the demo board. Make
sure the load current is set within spec, and the power
supply current capability is above 4A.
6. Once the proper output voltage is established, adjust the
input and load within the operating range and observe
the output voltage regulation, ripple voltage, efficiency
and other parameters. Typical efficiency curve, regula-
tion, and operation waveforms are shown in Figures 3
and 4, respectively.
NOTE: Whenmeasuringtheinputoroutputvoltageripples,
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
and GND, or VOUT and GND terminals. See Figure 2 for
proper scope probe technique.
4. Turn on the power supply at the input. Slowly increase
VIN to 3.0V.
NOTE: Make sure the input voltage is within the range. If
higher operating voltage is required, power components
with higher voltage ratings should be used. The maximum
input voltage of LT3759 is 42V.
NOTE: The output current capability depends on the input
voltage, as can be seen in Figure 3. Proper cooling is
necessary for overload operations.

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DEMO MANUAL DC1787A
QUICK START PROCEDURE
dc1787af F01
Figure 1. Proper Measurement Equipment Setup
Figure 2. Proper Scope Probe Placement for
Measuring Input or Output Ripple
Figure 3. Efficiency Curves Figure 4. Short Circuit Waveforms with Frequency Foldback
INPUT OR OUTPUT CAPACITOR
dc1787af F02
LOAD CURRENT (mA)
100 300 500 600 700 800200 400 900 1000
dc1787af F03
70
EFFICIENCY (%)
75
80
90
85
95
VIN = 12V
VIN = 4V
VIN = 2.8V
dc1787af F04
VO: 10V/DIV
VDS: 50V/DIV
ISW: 5A/DIV

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DEMO MANUAL DC1787A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 CIN1, CIN2 CAP., X7R, 10µF, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12L
2 1 CIN3 CAP., ELECT., 22µF, 50V, C-CE-BS-6.3X6.0 SUN ELECT., 50CE22BS
3 2 COUT1, COUT2 CAP., X5R, 47µF, 16V, 10%, 1210 MURATA, GRM32ER61C476KE15L
4 1 C1 CAP., X7R, 4.7µF, 50V, 20%, 1210 MURATA, GRM32ER71H475KA88L
5 1 C2 CAP., X7R, 1µF, 50V 10%, 0805 MURATA, GRM21BR71H105KA12L
6 1 C3 CAP., X5R, 4.7µF, 16V, 10%, 0805 MURATA, GRM219R61C475KE15D
7 1 C5 CAP., X7R, 68nF, 50V, 0603 NIC, NMC0603X7R682K50F
8 1 C6 CAP., X7R, 0.1µF, 25V, 10%, 0603 TDK, C1608X7R1E104K
9 1 C7 CAP., C0G, 470pF, 50V, 5%, 0603 MURATA, GCM1885C1H471JA16D
10 1 D3 DIODE, SCHOTTKY, 3A, POWERDI5 DIODES/ZETEX, PDS360-13
11 1 L1 IND, 15µH, L-DUAL-DRQ127 COILTRONICS, DRQ127-150-R
12 1 Q1 MOSFET, N-CHANNEL, LFPAK RENESAS, RJK0652DPB-00-J5
13 1 RCS RES SENSE, 0.005, 1/2W, 1%, 2010 VISHAY, WSL20105L000FEA
14 1 RFBB RES., CHIP, 15.8k, 1/16W, 1%, 0603 VISHAY, CRCW060315K8FKEA
15 1 RFBS RES., CHIP, 102k, 1/16W, 1%, 0603 VISHAY, CRCW0603102KFKEA
16 1 R1 RES., CHIP, 249k, 1/16W, 1%, 0603 VISHAY, CRCW0603249KFKEA
17 1 R2 RES., CHIP, 100k, 1/16W, 5%, 0603 VISHAY, CRCW0603100KJNEA
18 1 R3 RES., CHIP, 255k, 1/16W, 1%, 0603 VISHAY, CRCW0603255KFKEA
19 1 R4 RES., CHIP, 1.43k, 1/16W, 1%, 0603 VISHAY, CRCW06031K43FKEA
20 1 R5 RES., CHIP, 27.4k, 1/16W, 1%, 0603 VISHAY, CRCW060327K4FKEA
21 1 R6 RES., CHIP, 0, 0603 VISHAY, CRCW06030000Z0ED
22 1 U1 I.C. LT3759EMSE, MSE12 LINEAR TECH.,LT3759EMSE
Hardware/Components (For Demo Board Only)
1 7 E1, E2, E3, E4, E5, E6, E7 TESTPOINT, TURRET, .094" MILL-MAX, 2501-2-00-80-00-00-07-0
2 2 JP1, JP2 JMP, 3-PIN, 1 ROW .079CC SAMTEC, TMM-103-02-L-S
3 2 SHUNTS AS SHOWN ON
ASSY DWG
SHUNT, .079" CENTER SAMTEC, 2SN-BK-G
4 2 STENCILS BOTH SIDES DC1787A-2
Additional Demo Board Circuit Components
1 0 D1 DIODE, FAST SWITCHING, 1N4148WT, SOD523F OPT

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DEMO MANUAL DC1787A
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
CC B B
A A
ALL CAPACITORS ARE IN MICROFARADS, 0603.
NOTES: UNLESS OTHERWISE SPECIFIED
2. INSTALL SHUNTS AS SHOWN. 1. ALL RESISTORS ARE IN OHMS, 0603.
0.5A VIN > 2.8V 1A
*
*
VIN > 4V
EN/UVLO
PGOOD
VIN
+VOUT
+VOUT
+VOUT
SIZE DATE:
.VER.ONCI
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: [phone]
Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
LT3759EMSE
11MP25:21,1102/03/90
SEPIC CONVERTER WITH WIDE INPUT VOLTAGE RANGE
KIM T.
ZHONGMING Y.
N/A
DEMO CIRCUIT 1787A
SIZE DATE:
.VER.ONCI
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: [phone]
Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
LT3759EMSE
11MP25:21,1102/03/90
SEPIC CONVERTER WITH WIDE INPUT VOLTAGE RANGE
KIM T.
ZHONGMING Y.
N/A
DEMO CIRCUIT 1787A
SIZE DATE:
.VER.ONCI
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: [phone]
Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
LT3759EMSE
11MP25:21,1102/03/90
SEPIC CONVERTER WITH WIDE INPUT VOLTAGE RANGE
KIM T.
ZHONGMING Y.
N/A
DEMO CIRCUIT 1787A
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
ZHONGMING Y.
PRODUCTION109-30-11
_
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
ZHONGMING Y.
PRODUCTION109-30-11
_
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
ZHONGMING Y.
PRODUCTION109-30-11
_
E5 GND E5 GND
E4
EN/UVLO E4 EN/UVLO
Q1
RJK0652DPB
Q1
RJK0652DPB
2
4
53
1
D3
PDS360
D3
PDS360
2 1
3
CIN1 10uF 50V 1210 CIN1 10uF 50V 1210
E2
GND E2 GND
R4 1.43k R4 1.43k
COUT1 47uF 16V 1210 COUT1 47uF 16V 1210
JP1
RUN
SHDN
JP1
RUN
SHDN
1 3 2
COUT2 47uF 16V 1210 COUT2 47uF 16V 1210
C3
4.7uF 16V
0805
C3
4.7uF 16V
0805
R5 27.4k R5 27.4k
C2 1uF 50V 0805 C2 1uF 50V 0805
U1
LT3759EMSE
U1
LT3759EMSE
INTVCC
9
SS
3
VC
1
FBX 2
GND
13
EN/UVLO
12
RT
4
SYNC
5
VIN
11 DRIVE 10
PGOOD 6
SENSE 7
GATE 8
R1 249k R1 249k
CIN2 10uF 50V 1210 CIN2 10uF 50V 1210
C7 470pF C7 470pF
R6 0 R6 0
C6 0.1uF C6 0.1uF
L1B 15uH L1B 15uH
2 4
E6 +VOUT
12V /
E6 +VOUT
12V /
JP2
ON OFF
SYNC
JP2
ON OFF
SYNC
1 3 2
E1
VIN
2.8V - 36V
E1
VIN
2.8V - 36V L1A
15uH
DRQ127-150-R
L1A 15uH
DRQ127-150-R
1 3
+
CIN3 22uF 50V
SUN ELECT 50CE22BS
+
CIN3 22uF 50V
SUN ELECT 50CE22BS
E7 SYNC E7 SYNC
RFBB 15.8k RFBB 15.8k
E3
PGOOD E3 PGOOD
C1
4.7uF
50V
1210
C1
4.7uF
50V
1210
RCS 0.005 2010 RCS 0.005 2010
R3 255k R3 255k
RFBS 102k RFBS 102k
C5 68nF C5 68nF
R2 100k R2 100k
D1
OPT
1N4148WT
D1
OPT
1N4148WT
12

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DEMO MANUAL DC1787A
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2011
LT 1111 • 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:
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1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation