1
dc1881af
DEMO MANUAL DC1881A
DESCRIPTION
LTC3789EUFD
High Efficiency Compact
Buck-Boost Converter
Demonstration circuit 1881A is a high efficiency syn-
chronous buck-boost DC/DC converter with 6V to 36V
input range. It can supply 2.5A maximum load current at
12V output. The demo board features the LTC
®
3789EUFD
controller. The constant-frequency current mode architec-
ture allows a phase-lockable frequency of up to 600kHz,
while an optional output current feedback loop provides
support for applications such as battery charging. With a
wide input range, wide output range and seamless trans-
fers between operation modes, the LTC3789 is ideal for
automotive, telecom, distributed DC power systems and
battery-powered applications. This board has a compact
solution size with dual SO-8 MOSFETs, small inductor and
capacitor footprints. The package of LTC3789EUFD is a
small, low thermal impedance 4mm × 5mm 28-Lead QFN.
L, LT, LTC, LTM, μModule, 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 light load operation mode of the converter is determined
with the MODE/PLLIN pin. Use the JP2 jumper to select
pulse skipping mode or forced continuous mode (CCM)
operation. Switching frequency is preset at about 400kHz.
The converter can also be externally synchronized through
the MODE/PLLIN pin (PLLIN terminal on the board). To
shut down the converter, one simple way is to force the
RUN pin below 1.2V (JP1: OFF). The power good output
(PGOOD terminal) is low when the output voltage is outside
of the ±10% regulation window.
Design files for this circuit board are available at
http://www.linear.com/demo
Specifications are at TA = 25°C
PARAMETER CONDITION VALUE
Input Voltage Range 6V to 36V
Output Voltage, VOUT VIN = 6V to 36V, IOUT = 0A to 2.5A 12V ±2%
Maximum Output Current, IOUT VIN = 6V to 36V, VOUT = 12V 2.5A
Typical Output Ripple VIN = 36V, IOUT = 12A (20MHz BW) 44mVP-P
Typical Efficiency VIN = 12V, VOUT = 12V, IOUT = 2.5A 97.2%
Typical Switching Frequency 400kHz
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dc1881af
DEMO MANUAL DC1881A
QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup
Demonstration circuit 1881A is easy to set up to evaluate
the performance of the LTC3789. Refer to Figure 1 for
the proper measurement equipment setup and follow the
procedure below:
1. With power off, connect the input power supply to VIN
(6V to 36V) and GND (input return).
2. Connect the 12V output load between VOUT and GND
(Initial load: no load).
3. Connect the DVMs to the input and outputs.
4. Turn on the input power supply and check for the proper
output voltages. VOUT should be 12V ±2%.
5. Once the proper output voltages are established, ad-
just the loads within the operating range and observe
the output voltage regulation, ripple voltage and other
parameters.
Note: When measuring the output or input voltage ripple,
do not use the long ground lead on the oscilloscope probe.
See Figure 2 for the proper scope probe technique. Short,
stiff leads need to be soldered to the (+) and (–) terminals
of an output capacitor. The probe’s ground ring needs to
touch the (–) lead and the probe tip needs to touch the
(+) lead.
Additional Notes:
1. Usually, the worst case efficiency at full load is at 6VIN.
The board can deliver more output power at higher VIN.
2. R2 is needed for additional/constant output current
limit only.
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dc1881af
DEMO MANUAL DC1881A
QUICK START PROCEDURE
Figure 2. Measuring Output Voltage Ripple
Figure 3. Efficiency vs Load Current (VO = 12V, CCM)
+–
VOUT GND
COUT
LOAD CURRENT (A)
0
EFFICIENCY (%)
100
90
95
85
DC1881 F03
2.51.0 2.00.5 1.5
VIN = 36V
VIN = 24V
VIN = 12V
VIN = 6V
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 CC1 CAP., C0G, 100pF, 50V, 10% 0603 AVX, 06035A101KAT2A
2 1 CC2 CAP., X7R, 0.01μF, 50V, 10% 0603 AVX, 06035C103KAT2A
3 1 CSS CAP., X7R, 0.1μF, 50V, 10% 0603 AVX, 06035C104KAT2A
4 1 C15 CAP., X7R, 1μF, 50V, 10% 0805 AVX, 08055C105K
5 2 C7, C8 CAP., X7R, 0.1μF, 50V, 10% 0603 AVX, 06035C104K
6 1 CF CAP., X7R, 22pF, 50V, 10% 0603 AVX, 06035C220K
7 1 C11 CAP., NPO, 68pF, 50V, 10% 0603 AVX, 06035A680KAT2A
8 1 C10 CAP., X5R, 2.2μF, 16V, 10% 0603 TDK, C1608X5R1C225K
9 1 C24 CAP., X5R, 1μF, 16V, 10% 0603 AVX, 0603YD105KAT2A
10 4 C16, C17, C19, C20 CAP., X7R, 22μF, 16V, 20% 1210 AVX, 1210YC226MAT2A
11 2 C4, C22 CAP., X7R, 0.22μF, 16V, 20% 0603 AVX, 0603YC224MAT2A
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dc1881af
DEMO MANUAL DC1881A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
12 3 C9, C25, C26 CAP., X7R, 10μF, 50V, 20% 1210 TDK, C3225X7S1H106M
13 1 C18 CAP., X5R, 10μF, 6.3V, 20% 1206 AVX, 12066D106MAT2A
14 4 D4-D7 SCHOTTKY REC., DFLS160, POWER DI-123 DIODE INC., DFLS160
15 1 D8 ZENER DIODE, 5.1V, BZX84C5V1, SOT23 DIODES INC., BZX84C5V1-7-F
16 1 L1 INDUCTOR, 5.6μH COILCRAFT, XAL7070-562ME
17 2 Q1, Q2 DUAL N-CHANNEL MOSFET, SO-8 VISHAY, Si4288DY-T1-E3
18 1 RC RES., CHIP, 13k, 1/10W, 1% 0603 VISHAY, CRCW060313K0FKEA
19 1 RFB1 RES., CHIP, 113k, 1/10W, 1% 0603 YAGEO, RC0603FR-07113KL
20 1 RFB2 RES., CHIP, 8.06k, 1/10W, 1% 0603 YAGEO, RC0603FR-078K06L
21 1 R18 SENSOR RES., 0.015Ω, 1W, 1%, 2512 THIN FILM TECH., RL3720WT-R015-F
22 1 R2 SENSOR RES., 0.015Ω, .25W, 1%, 1206 VISHAY, WSL1206R0150FEA
23 6 R3, R4, R9, R10, R13, R14 RES., CHIP, 100Ω, 1/10W, 1% 0603 YAGEO, RC0603FR-07100RL
24 1 R7 RES., CHIP, 100k, 1/10W, 1% 0603 YAGEO, RC0603FR-07100KL
25 1 R8 RES., CHIP, 10Ω, 1/10W, 5% 0603 YAGEO, RC0603JR-0710RL
26 1 R26 RES., CHIP, 10Ω 1/8W, 5% 0805 YAGEO, RC0805JR-0710RL
27 1 R5 RES., CHIP, 10Ω 1/8W, 5% 0805 YAGEO, RC0805JR-0710RL
28 6 R1, R11, R17, R23, R25, R27 RES., CHIP, 0Ω, 1/10W, 1% 0603 YAGEO, RC0603FR-070RL
29 1 R20 0Ω JUMPER, 1/4W, 1206 IRC
30 1 R16 RES., CHIP, 1k, 1/10W, 1% 0603 YAGEO, RC0603FR-071KL
31 1 R24 RES., CHIP, 10k, 1/10W, 1% 0603 YAGEO, RC0603FR-0710KL
32 1 R21 RES., CHIP, 121k, 1/10W, 1% 0603 YAGEO, RC0603FR-07121KL
33 1 R30 RES., CHIP, 41.2k, 1/10W, 1% 0603 YAGEO, RC0603FR-0741K2L
34 1 R31 RES., CHIP, 12.1k, 1/10W, 1% 0603 YAGEO, RC0603FR-0712K1L
35 1 U1 I.C., VOLT. REG. LINEAR TECH. CORP. LTC3789EUFD
Additional Demo Board Circuit Components
1 0 CF1 (OPT) CAP., 0603
2 0 COUT1 (OPT) CAP., OS-CON, 330μF, 16V, 20% SANYO, 16SEP330M+T
3 0 C14, C23, C29 C35 (OPT) CAP., 1210
4 0 C12, C13 (OPT) CAP., 1206
5 0 R6, R12, R22 (OPT) RES., 0603
6 0 R28, R29 (OPT) RES., CHIP, 1206
Hardware: For Demo Board Only
1 2 JP1, JP2 3-PIN 0.079" SINGLE ROW HEADER SAMTEC, TMM103-02-L-S
2 2 XJP1, XJP2B SHUNT, 0.079" CENTER SAMTEC, 2SN-BK-G
3 9 TP3-TP7, TP10-TP14 TESTPOINT, TURRET, 0.094" pbf MILL-MAX, 2501-2-00-80-00-00-07-0
4 4 (STAND-OFF) STAND-OFF, NYLON 0.50" KEYSTONE, 8833 (SNAP ON)
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dc1881af
DEMO MANUAL DC1881A
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
16V
6.3V
MODE
CCM
PULSE SKIP
XAL7070
0805
50V
50V
NOTE: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS ARE 0603.
ALL CAPACITORS ARE 0603.
VOS+
VOS+
VOUT
VIN+
VOUT
INTVCC
INTVCC
VIN+
VOUT1
INTVCC
VIN+
INTVCC
VOUT
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 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
Tuesday, May 15, 2012
11
HIGH EFFICIENCY COMPACT BUCK-BOOST CONVERTER
HZ
CHARLIE Z.
N/A
LTC3789EUFD
DEMO CIRCUIT 1881A
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 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
Tuesday, May 15, 2012
11
HIGH EFFICIENCY COMPACT BUCK-BOOST CONVERTER
HZ
CHARLIE Z.
N/A
LTC3789EUFD
DEMO CIRCUIT 1881A
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 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
Tuesday, May 15, 2012
11
HIGH EFFICIENCY COMPACT BUCK-BOOST CONVERTER
HZ
CHARLIE Z.
N/A
LTC3789EUFD
DEMO CIRCUIT 1881A
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
CHARLIE Z.PRODUCTION
2 4-23-12
__
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
CHARLIE Z.PRODUCTION
2 4-23-12
__
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
CHARLIE Z.PRODUCTION
2 4-23-12
__
R11 0R11 0
R17 0R17 0
C4
0.22uF
16V
C4
0.22uF
16V
C26
10uF
50V
1210
C26
10uF
50V
1210
C10
2.2uF
C10
2.2uF
R27 0R27 0
R29
(OPT)
R29
(OPT)
C22
0.22uF
16V
C22
0.22uF
16V
Q2A
Si4288DY
Q2A
Si4288DY
4
3 5
6
TP12
EXTVCC TP12
EXTVCC
C29C29C17
22uF
16V
C17
22uF
16V
CF1 OPTCF1 OPT
CC2
0.01uF
CC2
0.01uF
Q1B
Si4288DY
Q1B
Si4288DY
2
1 7
8
R7
100K
R7
100K
R5
10
R5
10
R9 100
R9 100
R25
0
R25
0
R14
100
R14
100
R10 100
R10 100
R8
10
R8
10
C23
(OPT)
1210
C23
(OPT)
1210
C13
(OPT)
C13
(OPT)
JP1
ON
OFF
RUN
JP1
ON
OFF
RUN 1
3
2
RC
13K
RC
13K
R6 OPT
R6 OPT
R28
(OPT)
1206
R28
(OPT)
1206
R1 0R1 0
C18 10uFC18 10uF
U1
LTC3789EUFD
U1
LTC3789EUFD
VFB
26
SS
27
SENSE1+
28
SENSE1-
1
ITH
2
SGND
3
MODE/PLLIN
4
FREQ
5
RUN
6
VINSNS
7
VOUTSNS
8
ILIM
9
IOSENSE+
10
IOSENSE-
11
TRIM
12
SW2
13
TG2
14
BOOST2
15
BG2
16
EXTVCC
17
INTVCC
18
VIN
19
PGND
21
BOOST1
22
SW1
24
PGOOD
25
TG1
23
BG1
20
SGND
29
TP6
VIN
6V - 36VTP6
VIN
6V - 36V
CSS
0.1uF
CSS
0.1uF
R16 1KR16 1K
D7
DFLS160
D7
DFLS160
D6
DFLS160
D6
DFLS160
JP2JP2
1
3
2
C7 0.1uFC7 0.1uF
+
COUT1
OPT
16V
+
COUT1
OPT
16V
C35
(OPT)
1210
C35
(OPT)
1210
C11
68pF
C11
68pF
D5
DFLS160
D5
DFLS160
D8
BZX84C5V1
D8
BZX84C5V1
RFB2 8.06KRFB2 8.06K
TP3 VIN+
TP3 VIN+
R2 0.015
0.25W
R2 0.015
0.25W C19
22uF
16V
1210
C19
22uF
16V
1210
R18
0.015
1W
R18
0.015
1W
R24
10K
R24
10K
R12 OPTR12 OPT
C16
22uF
16V
1210
C16
22uF
16V
1210
TP5
SS TP5
SS
L1 5.6uHL1 5.6uH
R23 0R23 0
TP7 GND
TP7 GND
Q2B
Si4288DY
Q2B
Si4288DY
2
1 7
8
R21
121K
R21
121K
R26
10
R26
10
R30
41.2K
R30
41.2K
TP13
VOUT
12V / 2.5A MAXTP13
VOUT
12V / 2.5A MAX
C12
(OPT)
1206
C12
(OPT)
1206
C14
(OPT)
1210
C14
(OPT)
1210
R3 100R3 100
C9
10uF
C9
10uF
C8 0.1uFC8 0.1uF
CC1 100pF
CC1 100pF
R22
OPT
R22
OPT
C15
1uF
50V
0805
C15
1uF
50V
0805
TP4
PGOOD TP4
PGOOD
Q1A
Si4288DY
Q1A
Si4288DY
4
3 5
6
C25
50V
1210
C25
50V
1210
CF
22pF
CF
22pF
R20 0R20 0
R13
100
R13
100
C20C20
RFB1
113K
RFB1
113K
C24
1uF
C24
1uF
TP14 GND
TP14 GND
R4 100R4 100
R31
12.1K
R31
12.1K
TP10
PLLIN TP10
PLLIN
D4
DFLS160
D4
DFLS160
6
dc1881af
DEMO MANUAL DC1881A
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 0612 • 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
Copyright © 2004, Linear Technology Corporation
