Linear Technology DC1940A Quick setup guide

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dc1940af
DEMO MANUAL DC1940A
DESCRIPTION
Low Quiescent Current,
High Voltage Step-Down
Converter
Demonstration circuit 1940A is a low quiescent current,
synchronousbuckconverterfeaturingtheLTC
®
3891EUDC.
This demo board converts a 16V to 60V voltage to a 12V
at 15A output.
The main features of this board include an internal LDO
for gate drive power from VIN or EXTVCC, RUN and
PGOOD pins, a mode selector that allows the converter
to run in constant current mode (CCM), pulse-skipping or
Burst Mode
®
operation, and selectable current limit. The
DC1940Asupportsanadjustableoutputvoltage,soft-start
andtracking. The wide input voltage range of 16V to60V is
suitable for double battery automotive and distributed DC
power systems where low quiescent current is important.
The LTC3891 data sheet gives a complete description of
this part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 1940A.
The 60V avalanche rated MOSFETs, which are used
on DC1940A, can be operated at their rated voltage.
However, if application derating requirements are
stricter, MOSFETs with higher voltage rating can be used.
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
Please note, MOSFETs with higher voltage ratings may af-
fect the efficiency. If 60V MOSFETs are used, the MOSFET
avalanche rating and testing is typically done with 30%
over voltage margin (78V for 60V rated MOSFET). Please
check with particular MOSFET manufacturer to ensure the
avalanche voltage rating.
The DC1940A supports the following MOSFET packages:
LFPAK, PowerPAK SO-8 and Power 56. The subsequent
logic level (SV gate) MOSFETs can be used with DC1940A.
Si7850DP Vishay
RJK0651DPB Renesas
HAT2266H Renesas
BSC100N06LS3 G Infineon
FDMS86520L Fairchild
For synchronization to an external clock, remove jumper
JP2 and apply sync signal on terminal SYNC.
Design files for this circuit board are available at
http://www.linear.com/demo
(TA= 25°C)
PARAMETER CONDITIONS VALUE UNITS
Minimum Input Supply Voltage 16 V
Maximum Input Supply Voltage 60 V
Output Voltage Range VIN = 16V to 60V, IOUT1 = 0A to 5A 12 ± 2% V
Typical Switching Frequency 125 kHz
Typical Output Ripple (VOUT, 12V) ILOAD = 15A 80 mV
Efficiency Typical (VOUT, 12V) 97 %
Supply Quiescent Current VIN = 24V; VOUT = 12V, IO= 0A, Burst Mode Operation 50.8 μA
Supply Shutdown Current VIN = 24V 14.7 μA

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dc1940af
DEMO MANUAL DC1940A
QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup
Demonstration circuit 1940A is easy to set up to evaluate
the performance of the LTC3891EUDC. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below:
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.
1. Place jumper JP1 in the ON position.
2. With power off, connect the input power supply to VIN
and GND.
3. Turn on the power at the input. Check for the proper
output voltages:
V
OUT1 = 11.9V to 12.4V
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
4. Once the proper output voltages are established, adjust
the load within the operating range and observe the
output voltage regulation, ripple voltage, efficiency and
other parameters.
DC1940a F01

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dc1940af
DEMO MANUAL DC1940A
Figure 2. Measuring Input or Output Ripple
Figure 3. 12V Output, Efficiency vs Load, Burst Mode Operation, VIN 16V, 24V, 48V
QUICK START PROCEDURE
DC1940a F02
GND VIN
LOAD (A)
89
93
92
91
90
EFFICIENCY (%)
95
94
97
96
98
99
DC1940a F03
0.01 0.1 1 10 100
16V
24V
48V

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dc1940af
DEMO MANUAL DC1940A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 3 C1, C2, C10 CAP, X7R, 2.2μF 100V 10%, 1812 TDK, C4532X7R2A225K
2 1 C3 CAP, EL, 56μF/63V, F4 SUN EL, 63HVH56M
3 1 C4 CAP, X7R, 0.1μF 100V 10%, 0603 MURATA, GRM188R72A104KA35D
4 1 C5 CAP, NPO,10pF, 50V, 5%, 0603 AVX, 06031A100JAT2A
5 2 C9, C13 CAP, X7R, 0.1μF 50V 10%, 0603 TDK, C1608X7R1H104K
6 1 C6 CAP, X5R, 4.7μF, 16V, 10%, 0805 MURATA, GRM219R61C475KE15D
7 2 C7, C17 CAP, X7R, 1μF 16V, 10%, 0603 TDK, C1608X7R1C105K
8 1 C8 CAP, NPO, 2.2pF 50V, ±0.25pF, 0603 AVX, 06035A2R2CAT
9 1 C12 CAP, X7R, 4700pF, 10V, 5%, 0603 AVX, 0603ZC472JAT2A
10 1 C14 CAP, NPO, 47pF 50V, 5%, 0603 NIC, NMC0603NPO470J50TRPF
11 1 C15 CAP, X7R, 10μF 16V 10%, 1206 MURATA, GCM31CR71C106KA64L
12 1 C16 CAP, SANYO, 150μF, 16V, 20% SANYO, 16TSVPC150
13 1 D1 DIODE, POWER DI-123 DIODES/ZETEX, DFLS1100-7
14 1 L1 IND, 10μH, 7443631000 WÜRTH, 7443631000
15 1 Q1 SILICON N CHANNEL POWER MOSFET LFPAK RENESAS, RJK0651DPB
16 1 Q2 SILICON N CHANNEL POWER MOSFET LFPAK RENESAS, RJK0653DPB
17 1 RS1 RES, 0.003Ω 1W 1% 2512 PANASONIC ERJM1WSF3M0U
18 1 R1 RES, 2.2 1% 1/10W, 0603 VISHAY, CRCW06032R20FNEA
19 3 R2, R8, R10 RES, 0Ω 1% 1/16W, 0603 VISHAY, CRCW06030000Z0EA
20 2 R4, R20 RES, 100k 1% 1/16W, 0603 VISHAY, CRCW0603100KFKEA
21 1 R5 RES, 511k 1% 1/16W, 0805 VISHAY, CRCW0805511KFKEA
22 1 R6 RES, 30.1k 1% 1/10W, 0603 VISHAY, CRCW060330K1FKEA
23 1 R7 RES, 35.7k 1% 1/16W, 0603 VISHAY, CRCW060335K7FKEA
24 1 R13 RES, 100 1% 1/10W, 0603 VISHAY, CRCW0603100RFKEA
25 1 R14 RES, 1M 1% 1/10W, 0805 VISHAY, CRCW08051M00FKEA
26 1 R15 RES, 2Ω 1% 1/16W, 0603 VISHAY, CRCW06032R00FNEA
27 1 R16 RES, 57.6k 1% 1/16W, 0603 VISHAY, CRCW060357K6FKEA
28 1 R17 RES, 15.4k 1% 1/10W, 0603 VISHAY, CRCW060315K4FKEA
29 1 R18 RES, 1k 1% 1/16W, 0603 VISHAY, CRCW06031K00FKEA
30 1 U1 IC, LTC3891EUDC, QFN20EUDC-3X4 LINEAR TECHNOLOGY, LTC3891EUDC
Additional Demo Board Circuit Components
1 R3, R9, R11, C11, R12,
C18, C19, R19, R21 RES, 0603 OPT
2 C20, C21, C22 CAP, 7343 OPT
3 Q3, Q4 (OPT) MOSFET, LFPAK OPT
Hardware
1 10 E1 TO E10 TESTPOINT, TURRET, 0.094" MILL-MAX, 2501-2-00-80-00-00-07-0
2 4 J1, J2, J3, J4 CONN, BANANA JACK, KEYSTONE-575-4 KEYSTONE 575-4
31JP1 JMP, 3PIN 1 ROW, 0.079" SULLINS, NRPN031PAEN-RC
41JP2 JMP, 3PIN 2 ROW, 0.079" SULLINS, NRPN032PAEN-RC
5 4 MTGS AT 4 CORNERS STANDOFF, NYLON 0.5 1/2" KEYSTONE, 8833(SNAP-ON)
6 2 XJP1, XJP2 SHUNT, 0.079" CENTER SAMTEC, 2SN-BK-G

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dc1940af
DEMO MANUAL DC1940A
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:
12V / 15A
16 - 60V
RUN
ON OFF
BURST
FCM
MODE
3. FOR SYNCHRONIZATION REMOVE JUMPER JP2 'MODE' AND CONNECT SOURCE OF THE SYNC SIGNAL TO TERMINALS E8 'SYNC' AND E9 'GND'
PULSE SKIP
1. ALL RESISTORS AND CAPACITORS ARE 0603 2. INSTALL SHUNTS AS SHOWN.
63HVH56M
SUN ELECT.
INTVCC
VIN
INTVCC
VOUT
VIN
VOUT
VIN
INTVCC
VOUT
INTVCC
INTVCC
INTVCC
VIN
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
VICTOR K.PRODUCTION2 03-26-12
__
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
VICTOR K.PRODUCTION2 03-26-12
__
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
VICTOR K.PRODUCTION2 03-26-12
__
SIZE DATE:
IC NO. REV.
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
Monday, March 26, 2012
11
LOW QUIESCENT CURRENT HIGH VOLTAGE STEP-DOWN CONVERTER
LT
VICTOR K
N/A
LTC3891EUDC
DEMO CIRCUIT 1940A
SIZE DATE:
IC NO. REV.
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
Monday, March 26, 2012
11
LOW QUIESCENT CURRENT HIGH VOLTAGE STEP-DOWN CONVERTER
LT
VICTOR K
N/A
LTC3891EUDC
DEMO CIRCUIT 1940A
SIZE DATE:
IC NO. REV.
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
Monday, March 26, 2012
11
LOW QUIESCENT CURRENT HIGH VOLTAGE STEP-DOWN CONVERTER
LT
VICTOR K
N/A
LTC3891EUDC
DEMO CIRCUIT 1940A
R8 0 R8 0
R17
15.4K
R17
15.4K
C9
0.1uF
C9
0.1uF
R3 OPT R3 OPT
C11
OPT
C11
OPT
D1
DFLS1100
D1
DFLS1100
E10
GND
E10
GND
Q1
RJK0651DPB Q1 RJK0651DPB
3
1
2
4
5
R2
0
R2
0
C13
0.1uF
50V
C13
0.1uF
50V
R16
57.6K
R16
57.6K
J3
VOUT
J3
VOUT
E2
GND
E2
GND
R21 OPT R21 OPT
C19 OPT C19 OPT
+
C20 OPT 7343
+
C20 OPT 7343
RS1
0.003
2512 RS1
0.003
2512
R15
2
R15
2
Q4
OPT
Q4
OPT
3
1
2
4
5
C18
OPT
C18
OPT
R18 1K R18 1K
C10
2.2uF
100V
1812
C10
2.2uF
100V
1812
C17
1uF
C17
1uF
C2 2.2uF 100V 1812 C2 2.2uF 100V 1812
E7 GND E7 GND
J2
GND J2 GND
R13
100
R13
100
C6
4.7uF
0805
C6
4.7uF
0805
R11
OPT
R11
OPT
R7 35.7K R7 35.7K
E4
EXTVCC
E4
EXTVCC
JP2JP2
1 3
2 4
5 6
R6
30.1K
R6
30.1K
J4 GND J4 GND
E1
VIN E1 VIN
C7 1uF C7 1uF
C1 2.2uF 100V 1812 C1 2.2uF 100V 1812
C12
4.7nF
C12
4.7nF
R12 OPT R12 OPT
+
C16
150uF 16V
16SVPC150M
+
C16
150uF 16V
16SVPC150M
E6 VOUT E6 VOUT
C5 10pF C5 10pF
C15
10uF
1206
C15
10uF
1206
U1 LTC3891EUDC U1 LTC3891EUDC
VIN
17
PGOOD
9
EXTVCC
15
TRACK/SS
19
RUN
4
ITH
8
SGND
2
SGND
3
PGND
16
PLLIN/MODE
1
ILIM
18 BG 13
SW 11
TG 10
BOOST 12
SENSE+ 6
SENSE- 5
INTVCC 14
VFB 7
FREQ 20
SGND
21
Q3
OPT
Q3
OPT
3
1
2
4
5
+
C3 56uF/63V
+
C3 56uF/63V
L1
10uH
L1
10uH
C8
2.2pF
C8
2.2pF
+
C22 OPT 7343
+
C22 OPT 7343
R14
1 Meg
0805 R14
1 Meg
0805
E3
PGOOD
E3
PGOOD
J1
VIN J1 VIN
R4
100k
R4
100k
Q2
RJK0653DPB
Q2
RJK0653DPB
3
1
2
4
5
R5 511K 0805 R5 511K 0805
JP1JP1
1 3 2
R9
OPT
R9
OPT
E5
TRACK
E5
TRACK
+
C21 OPT 7343
+
C21 OPT 7343
E8
SYNC
E8
SYNC
R19 OPT R19 OPT
R20
100K
R20
100K
R1 2.2 R1 2.2
E9
GND
E9
GND
C14
47pF
C14
47pF
R10
0
R10
0
C4 0.1uF 100V C4 0.1uF 100V

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dc1940af
DEMO MANUAL DC1940A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●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:
Thisdemonstrationboard(DEMOBOARD)kitbeingsoldorprovidedbyLinear Technologyis intended for useforENGINEERING 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.
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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,
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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.
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