1
dc1537af
DEMO MANUAL DC1537A
DESCRIPTION
LT3992A
Monolithic Dual Tracking 3A
Step-Down Switching Regulator
The demo circuit 1537A is a dual current mode PWM
step-down DC/DC converter featuring LT
®
3992. The demo
circuit is designed for 5V and 3.3V outputs from a 7V to
60V input. The current capability of each channel is up to 3A
when running individually and 2A when both are sourcing
the same current without special heat sinking. Individual
soft-start, current limit, comparator, input voltage for each
output as well as frequency division and synchronous
and clock output functions simplify the complex design
of dual-output power converters
Both converters are synchronized to either a common
external clock input or a resistor programmable 250kHz to
2MHz internal oscillator. At all frequencies, a 180° phase
shift between channels is maintained, reducing voltage
ripple. Programmable frequency allows optimization be-
tween efficiency and external component size. Each output
can be independently disabled using its own SHDN pin
and be placed in a low quiescent current shutdown mode.
The LT3992 data sheet gives complete description of the
device, operation and application information. The data 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
sheet must be read in conjunction with this quick start
guide for demo circuit 1537A.
Design files for this circuit board are available at
http://www.linear.com/demo
Specifi cations are at TA = 25°C.
PARAMETER CONDITIONS VALUE
Minimum Input Voltage 7V
Maximum Input Voltage 60V (For Transient. Continuous Operation
if D3 and D4 Are Replaced with Higher
Voltage Rated Schottky Diodes)
Output Voltage VOUT1 V
IN = 7~ 60V 5.0V ±3%
Output Voltage VOUT2 VIN = 7~ 60V 3.3V ±3%
Switching Frequency 300kHz ±10%
Maximum Output Current IOUT1 VIN = 7~ 60V 3A Individually, 2A Both Running
Maximum Output Current IOUT2 VIN = 7~ 60V 3A Individually, 2A Both Running
Voltage Ripple VOUT1 VIN = 12V, IOUT1 = 3A <20mV
Voltage Ripple VOUT2 VIN = 12V, IOUT2 = 3A <20mV
Figure 1. Single Channel Efficiency at VIN = 24V,
f = 300kHz
LOAD CURRENT FOR SIGNAL CHANNEL (A)
0.3
EFFICIENCY (%)
90
95
100
1.2 2.1
DC1537a F01
85
80
0.6 0.9 1.81.5 2.4 2.7 3.0
75
70
65
60
VOUT1 = 5V
VOUT2 = 3.3V
2
dc1537af
DEMO MANUAL DC1537A
QUICK START PROCEDURE
Demo circuit 1537A is easy to set up to evaluate the
performance of the LT3992. Refer to Figure 5 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 6 for
proper scope probe technique.
1. Place JP1 on the SINGLE position.
2. With power off, connect the input power supply to VIN1
and GND. (Connect another input power supply to VIN2
and GND if DUAL is selected.)
3. Turn on the power at the input.
NOTE. Make sure that the input voltage does not exceed
60V (Due to part selection on D3 and D4, 60V is for
transient purpose. Continuous operation can be avail-
able after D3 and D4 are replaced with higher voltage
rated schottky diodes).
4. Check for the proper output voltages.
NOTE. If there is no output, temporarily disconnect
the load to make sure that the load is not set too high.
5. 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.
ADDITIONAL NOTES
If an EMI filter is desirable on VIN1, it can be feasibly
installed on the back of the board in the optional circuit
area. However, a trace cut is required for the insertion of
the optional circuit. See Figure 7 for the cut line.
DESCRIPTION
LOAD CURRENT FOR BOTH CHANNELS (A)
0.2
EFFICIENCY (%)
90
95
100
0.8 1.4
DC1537a F02
85
80
0.4 0.6 1.21.0 1.6 1.8 2.0
75
70
65
60
VIN (V)
5
TJ PIN VOLTAGE (V)
0.8
0.9
30
DC1537a F04
0.7
10 15 2520 35 40
0.6
0.5
0.4
Figure 2. Dual Channel Efficiency
at VIN = 24V, f = 300kHz
Figure 3. DC1537A TJ Pin Voltage
When Channels Running Individually
at 3A Load (TA = 25°C)
Figure 4. DC1537A TJ Pin Voltage
When Both Channels Sourcing 2A
Current at Meantime (TA = 25°C)
VIN (V)
5
TJ PIN VOLTAGE (V)
0.8
0.9
30
DC1537a F03
0.7
10 15 2520 35 40
0.6
0.5
0.4
VOUT1 = 5V/3A, VOUT2 NO LOAD
VOUT2 = 3.3V/3A, VOUT1 NO LOAD
3
dc1537af
DEMO MANUAL DC1537A
QUICK START PROCEDURE
Figure 5. DC1537A Proper Equipment Setup
Figure 6. Measuring Input or Output Ripple
GND
VIN
Figure 7. Cut Line for the EMI Filter Installation
4
dc1537af
DEMO MANUAL DC1537A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 4 C2, C3, C22, C23 CAP, 1210 2.2μF 10% 100V X7R AVX 12101C225KAT2A
2 2 C4, C5 CAP, 0603 0.47μF 10% 25V X7R MURATA GRM188R71E474KA12D
3 2 C7, C8 CAP, 1210 100μF 20% 10V X5R TAIYO YUDEN LMK325ABJ107MM-T
4 2 C10, C11 CAP, 0402 22pF 10% 25V NPO AVX 04023A220KAT2A
5 2 C12, C13 CAP, 0402 0.1μF 10% 16V X7R TDK C1005X7R1C104K
6 2 C14, C15 CAP, 0402 680pF 10% 25V X7R AVX 04023C681KAT2A
7 2 C16, C17 CAP, 0402 33pF 10% 25V NPO AVX 04023A330KAT
8 1 C24 CAP, 0402 10nF 10% 16V X7R MURATA GRM155R71C103KA01D
9 2 D1, D5 DIODE, SCHOTTKY BARRIER SOD123 ON SEMICONDUCTOR MMSD701T1G
10 2 D2, D4 DIODE, SCHOTTKY RECTIFIER SMB DIODES INC. B360B
11 1 L1 IND, 22μH NIC NPIM104B220MTRF
12 1 L2 IND, 10μH NIC NPIM104B100MTRF
13 2 R1, R2 RES, 0603 1kΩ 1% 1/16W NIC NRC06F1001TRF
14 1 R5 RES, 0402 42.2kΩ 1% 1/16W VISHAY CRCW040242K2FKED
15 1 R6 RES, 0402 24.9kΩ 1% 1/16W VISHAY CRCW040224K9FKED
16 2 R7, R8 RES, 0402 100kΩ 5% 1/16W VISHAY CRCW0402100KJNED
17 2 R9, R10 RES, 0402 8.06kΩ 1% 1/16W VISHAY CRCW04028K06FKED
18 2 R11, R12 RES, 0402 100kΩ 1% 1/16W VISHAY CRCW0402100KFKED
19 2 R13, R14 RES, 0402 30kΩ 1% 1/16W NIC NRC04F3002TRF
20 1 R15 RES, 0402 7.32kΩ 1% 1/16W VISHAY CRCW04027K32FKED
21 1 R16 RES, 0402 20kΩ 1% 1/16W VISHAY CRCW040220K0FKED
22 1 R17 RES, 0402 40.2kΩ 1% 1/16W VISHAY CRCW040240K2FKED
23 1 U1 IC, STEP-DOWN REGULATOR LINEAR TECHNOLOGY LT3992EFE
Additional Demo Board Circuit Components
1 2 C1, C21 CAP, 22μF 20% 100V OSCON SUNCON 100CE22BS
2 0 C6, C9 CAP, 0805 10μF 10% 16V X5R OPTION MURATA GRM21BR61C106KE15L OPTION
3 0 C18 CAP, 22uF 20% 100V OSCON OPTION SANYO 100CE22BS OPTION
4 0 C19 CAP, 0603 0.01μF 10% 100V X7R OPTION AVX 06031C103KAT OPTION
5 0 C20 CAP, 1210 2.2μF 10% 100V X7R OPTION AVX 12101C225KAT2A OPTION
6 0 C25 CAP, 0402 10nF 10% 16V X7R OPTION MURATA GRM155R71C103KA01D OPTION
7 0 D3, D6 DIODE, SCHOTTKY BARRIER SOD123 OPTION ON SEMICONDUCTOR MMSD701T1G OPTION
8 0 D7, D8 DIODE, OPT OPTION
9 0 R18 RES, 0603 0Ω JUMPER OPTION VISHAY CRCW06030000Z0EA OPTION
10 0 FB1 FERRITE BEAD OPTION TAIYO YUDEN FBMJ3216HS800 OPTION
11 0 L3 IND, 22μH OPTION VISHAY IHLP4040DZ-01 OPTION
Hardware/Components (For Demo Board Only)
1 1 JP1 HEADER,4-PIN SAMTEC TMM-104-02-L-S
2 8 TP1, TP2, TP5 TO TP8,
TP16, TP17
TURRET MILL-MAX 2501-2-00-80-00-00-07-0
3 9 TP3, TP4, TP9 TO TP15 TURRET MILL-MAX 2308-2-00-80-00-00-07-0
4 1 JP1 SHUNT,2mm SAMTEC 2SN-BK-G
5
dc1537af
DEMO MANUAL DC1537A
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
9$
NOTES: UNLESS OTHERWISE SPECIFIED,
OPT
7V - 60V
OPT
237,21$/&,5&8,7
OPT
OPT
OPT OPT
OPT
OPT
7V - 60V
(300kHz)
OPT
[1] SEE QUICK START GUIDE FOR DETAILS ON JP1 SETTING
AND INPUT VOLTAGE IMPLEMENTATION ORDER.
OPT
[1]
2. ALL CAPACITORS ARE 0402.
ALL RESISTORS ARE 0402.
*
*
SEE QUICK START GUIDE FOR DETAILS ON
CURRENT CAPABILITY.
*
VOUT1 VOUT2
VOUT1
VIN1
VIN1 VIN2VOUT1
VIN1 VIN1
VIN2
VOUT2
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DUAL MONOLITHIC STEP-DOWN
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LT3992EFE
DEMO CIRCUIT 1537A
CONVERTER
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Tuesday, January 17, 2012
DUAL MONOLITHIC STEP-DOWN
JW
EDWIN L.
1$
LT3992EFE
DEMO CIRCUIT 1537A
CONVERTER
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6+((7 2)
7,7/(
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DUAL MONOLITHIC STEP-DOWN
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LT3992EFE
DEMO CIRCUIT 1537A
CONVERTER
REVISION HISTORY
DESCRIPTION DATE APPROVEDECO REV
EDWIN L.
PRODUCTION201-17-12
REVISION HISTORY
DESCRIPTION DATE APPROVEDECO REV
EDWIN L.
PRODUCTION201-17-12
REVISION HISTORY
DESCRIPTION DATE APPROVEDECO REV
EDWIN L.
PRODUCTION201-17-12
D7
OPT
D7
OPT
R1
1k
1%
0603
R1
1k
1%
0603
C3
2.2uF
100V
1210
C3
2.2uF
100V
1210
C24
10nF
C24
10nF
TP14
CLKOUT
TP14
CLKOUT
TP16
VIN2
TP16
VIN2
C2
2.2uF
100V
1210
C2
2.2uF
100V
1210
JP1
SINGLE
DUAL
INPUT MODE
CASCADE
JP1
SINGLE
DUAL
INPUT MODE
CASCADE
1
3
2
4
TP2
GND
TP2
GND
TP1
VIN1
TP1
VIN1
L2
10uH
L2
10uH
TP12
SS2
TP12
SS2
+
C21
22uF
100V
+
C21
22uF
100V
R15
7.32k
1%
R15
7.32k
1%
D1
MMSD701T1G
D1
MMSD701T1G
TP11
SS1
TP11
SS1
C23
2.2uF
100V
1210
C23
2.2uF
100V
1210
TP10
CMPO2
TP10
CMPO2
R2
1k
1%
0603
R2
1k
1%
0603
10uF
C6
16V
0805
10uF
C6
16V
0805
C17 33pFC17 33pF
R7
100K
R7
100K
U1
LT3992EFE
U1
LT3992EFE
SW1
38
DIV
27
VC2 26
SS2 24
FB1
9FB2 11
CMPI2 12
CMPO2 13
BST2 14
CMPI1
8
IND2 18
SW2 20
VIN2 22
SHDN2 23
VOUT2 16
CMPO1
7
BST1
6
ILIM1
33
TJ 28
CLKOUT 29
RT/SYNC
30
VC1
32
VOUT1
4
SHDN1
35
VIN1 36
PGND
39
SS1
34
IND1
2
ILIM2 25
NC
10
NC
15
NC 21
NC 31
NC
1
NC
3
NC
5
NC 17
NC 19
NC 37
D6
MMSD701T1G
D6
MMSD701T1G
C22
2.2uF
100V
1210
C22
2.2uF
100V
1210
+
C1
22uF
100V
+
C1
22uF
100V
C16 33pFC16 33pF
C4 0.47uF
0603
C4 0.47uF
0603
TP5
VOUT1
5V/2A TP5
VOUT1
5V/2A
TP15
TEMP
TP15
TEMP
100uF
C7
10V
1210
100uF
C7
10V
1210
D4
B360B
D4
B360B
R8
100K
R8
100K
R16
20k
1%
R16
20k
1%
R6
24.9K
1%
R6
24.9K
1%
100uF
C8
10V
1210
100uF
C8
10V
1210
TP8
GND
TP8
GND
D5
MMSD701T1G
D5
MMSD701T1G
L3 22uHL3 22uH
TP6
VOUT2
TP6
VOUT2
C12
0.1uF
C12
0.1uF
R11 100K 1%
R11 100K 1%
R14 30k 1%R14 30k 1%
R9 8.06K 1%R9 8.06K 1%
10uF
C9
16V
0805
10uF
C9
16V
0805
C5 0.47uF
0603
C5 0.47uF
0603
TP7
GND
TP7
GND
+
C18
22uF
100V
+
C18
22uF
100V
D2
B360B
D2
B360B
TP17
GND
TP17
GND
TP9
CMPO1
TP9
CMPO1
R10 8.06K 1%R10 8.06K 1%
C25
10nF
C25
10nF
C19
0.01uF
0603
100V
C19
0.01uF
0603
100V
C10
22pF
C10
22pF
TP13
SYNC
TP13
SYNC
D8
OPT
D8
OPT
C14 680pFC14 680pF
R17
40.2k
1%
R17
40.2k
1%
TP3
SHDN1
TP3
SHDN1
R18
OPT
R18
OPT
R5
42.2K
1%
R5
42.2K
1%
FB1 BEADFB1 BEAD
R13 30k 1%R13 30k 1%
C20
2.2uF
100V
1210
C20
2.2uF
100V
1210
L1
22uH
L1
22uH
TP4
SHDN2
TP4
SHDN2
R12 100K 1%R12 100K 1%
D3
MMSD701T1G
D3
MMSD701T1G
C11
22pF
C11
22pF
C13
0.1uF
C13
0.1uF
C15 680pFC15 680pF
6
dc1537af
DEMO MANUAL DC1537A
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 0212 • 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
