DC1727A - Demo Manual

DEMO MANUAL DC1727A
LT3641: Dual Monolithic
Buck Regulator with Power-On
Reset and Watchdog Timer
Description
Demonstration circuit 1727A is a dual monolithic buck
regulator with power-on reset and watchdog timer featuring
the LT3641. The board operates from inputs up to 42V and
withstands transients up to 55V. The outputs are 5V, 1A
and 1.8V, 0.8A. At light loads, both regulators operate in
low ripple Burst Mode® to maintain high efficiency and low
output ripple. Users can populate R13 on the EN/UVLO pin
and R14 on EN2 to provide a programmable under voltage
lockout for both outputs respectively. Both channels have
cycle-by-cycle current limit, providing protection against
shorted outputs.
The power-on reset and watchdog timer periods are independently adjustable using external capacitors. Tight
accuracy specifications and glitch immunity ensure reliable operation of the circuit. Watchdog can be enabled or
disabled by JP1.
Performance Summary
The circuit can be synchronized to an external clock connected to the SYNC terminal. If the SYNC function is used,
the RT resistor (R9) should be chosen to set the LT3641
internal switching frequency at least 20% below the lowest
synchronization input frequency.
The LT3641 data sheet gives complete descriptions of the
part, operation and application information. The data sheet
must be read in conjunction with this quick start guide for
working on or modifying the demo circuit 1727A.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, µModule, 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.
(TA = 25°C)
SYMBOL
PARAMETER
CONDITIONS
VIN
Input Supply Range
VOUT1 = 5V, IOUT1 = 1A
VOUT2 = 1.8V, IOUT2 = 0.8A
MIN
TYP
7
MAX
UNITS
42
V
VOUT1
Output Voltage 1
VIN = 12V, IOUT1 = 0.8A
4.92
5.07
5.22
V
VOUT2
Output Voltage 2
VIN = 12V, IOUT2 = 1A
1.746
1.8
1.854
V
IOUT1
Output Current 1
0
1
A
IOUT2
Output Current 2
0
0.8
A
IQ
No Load Quiescent Current
fSW
Switching Frequency
tWDU
Watchdog Upper Boundary Period
C7 = 1500pF
55.5
ms
tWDL
Watchdog Lower Boundary Period
C7 = 1500pF
3.5
ms
tRST
Programmed Reset Period
C8 = 1500pF
55.5
ms
VIN = 12V, VOUT1 = 5V, VOUT2 = 1.8V, No Load
0.37
1.75
2
mA
2.35
MHz
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DEMO MANUAL DC1727A
quick start procedure
Demonstration circuit 1727A is easy to set up to evaluate the performance of the LT3641. Refer to Figure 2 for
proper measurement equipment setup and follow the
procedure below:
1.Place Jumper JP1 in the following position:
OFF: Watchdog Disabled
ON: Watchdog Enabled
2.With power off, connect the input power supply to VIN
and GND.
5.Check for the proper output voltages:
VOUT1 = 5V, VOUT2 = 1.8V
Note: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high or
is shorted.
6. Once the proper output voltages are established, adjust
the loads within the operating range and observe the
output voltage regulation, ripple voltage, efficiency and
other parameters.
4.Turn on the power at the input.
7. To test the watchdog timer, place jumper JP1 in the ON
position. Connect a clock input to the WDI terminal.
Observe the output at the WDO terminal while the clock
parameters are adjusted.
Note: Make sure that the input voltage does not
exceed 42V.
8.To test Power-On Reset, observe output at the RESET
terminals: RST1 and RST2.
3.With power off, connect loads from VOUT1 to GND and
VOUT2 to GND.
95
2MHz, VIN = 12V
VOUT1 = 5V AT 1A, VOUT2 = 1.8V
TOTAL EFFICIENCY (%)
90
85
80
75
70
0
0.4
0.6
0.2
VOUT2 CURRENT (A)
0.8
DC1727A F01
Figure 1. Total Efficiency vs VOUT2 Current
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DEMO MANUAL DC1727A
Quick Start Procedure
Figure 2. DC1727A Proper Measurement Equipment Setup
Figure 3. Measuring Input or Output Ripple
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DEMO MANUAL DC1727A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
1
C1
Capacitor, X7R, 0.22µF, 10V, 10%, 0603
Murata, GRM188R71A224KA01D
2
1
C2
Capacitor, X7R, 4.7µF, 50V, 10%, 1206
Murata, GRM31CR71H475KA12L
3
2
C3, C4
Capacitor, X7R, 22µF, 6.3V, 20%, 1206
AVX, 12066C226MAT2A
4
2
C5, C6
Capacitor, X7R, 1000pF, 25V, 10%, 0603
AVX, 06033C102KAT2A
5
2
C7, C8
Capacitor, COG, 1500pF, 25V, 5%, 0603
Murata, GRM1885C1E152JA
6
1
D1
Diode, Schottky, Diode, SOD323
Central Semiconductor., CMDD6263
7
1
D2
Diode, Schottky, PowerDI123
DIODES/ZETEX, DFLS260-7
8
1
L1
Inductor, 4.7µH
Cooper Bussmann, MPI4040R3-4R7-R
9
1
L2
Inductor, 1.0µH
Cooper Bussmann, SD3812-1R0-R
10
2
R1, R12
Resistor, Chip, 301k, 1%, 0603
Vishay, CRCW0603301KFKED
11
3
R3, R5, R11
Resistor, Chip, 100k, 1%, 0603
Panasonic, ERJ3EKF1003V
12
1
R7
Resistor, Chip, 49.9k, 1%, 0603
Vishay, CRCW060349K9FKEA
13
1
R9
Resistor, Chip, 32.4k, 1%, 0603
Vishay, CRCW060332K4FKED
14
1
U1
IC, LT3641EFE#PBF, TSSOP (4.4mm)
Linear Technology, LT3641EFE#PBF
Suncom, 63CE22BS
Additional Demo Board Circuit Components
1
1
C9
Capacitor, Aluminum SMT, 22µF, 63V
2
0
C10 (Optional)
Capacitor, 0603
3
0
C11 (Optional)
Capacitor, 1210
4
0
FB1 (Optional)
Ferrite Bead, Chip, 1206
5
0
L3 (Optional)
Inductor, SMT Power Inductor
6
5
R2, R4, R6, R8, R10
Resistor, Chip, 100k, 1%, 0603
7
0
R13, R14 (Optional)
Resistor, 0603
Vishay, CRCW0603100KFKEA
Hardware: For Demo Board Only
1
16
E1-E16
Testpoint, Turret, .095"
Mill-Max, 2501-2-00-80-00-00-07-0
2
1
JP1
2mm Single Row Header, 3-Pin
Samtec, TMM-103-02-L-S
3
1
JP1
Shunt, 2mm
Samtec, 2SN-BK-G
4
4
MTGS
Stand-Off, Nylon 0.5" Tall
Würth, 702935000 (Snap On)
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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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
A
B
C
E10
E9
E15
E13
E6
E12
ON
OFF
100K
R4
VOUT1R6
JP1
2
R8
WDE
100K
5
2. INSTALL SHUNTS AS SHOWN.
1. ALL RESISTORS ARE IN 0603.
ALL CAPACITORS ARE IN 0603.
100K
100K
R13
(OPT)
R2
NOTE: UNLESS OTHERWISE SPECIFIED
RST2
RST1
GND
WDO
WDI
PGOOD2
E4 VOUT1
R11
100K
VOUT1
(OPT)
1
3
EN2
R14
E11
4
8
9
13
10
14
2
27
3
RST2
RST1
WDE
WDO
WDI
PGOOD2
EN2
EN/UVLO
C7
C8
1500pF 1500pF
11
22
VIN
GND
CWDT
R12
301K
C1 0.22uF
10V
U1
LT3641EFE
RT
7
C2
4.7uF
50V
1206
CPOR
12
20
SW
GND
R9
32.4K
29
21
GND
23
VIN
GND
26
BST
GND
1
SYNC
SS2
SS1
FB2
FB1
SW2
VIN2
DA
SW1
D1
3
4
28
5
1
6
25
24
18
GND
VEMI
E16
E14
3
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
JAINO P.
APP ENG.
2
SCALE = NONE
HZ
PCB DES.
APPROVALS
C10
(OPT)
0603
FB1
1
+ C9
22uF
63V
OPT
VIN
SYNC
GND
VOUT2
1.8V @ 0.8A
GND
VOUT1
5V @ 1A
JAINO P.
APPROVED
DATE:
1
SHEET 1
LT3641EFE
DEMO CIRCUIT 1727A
Wednesday, July 13, 2011
IC NO.
DATE
7-11-11
OF 1
1
REV.
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
PRODUCTION
DESCRIPTION
DUAL MONOLITHIC STEP-DOWN SWITCHING REGULATOR WITH
POWER-ON RESET AND WATCH DOG TIMER
N/A
SIZE
TITLE: SCHEMATIC
C11
(OPT)
1210
OPT
L3
LPS4018-332ML
R10
100K
E8
E7
E5
E3
1
REVISION HISTORY
TECHNOLOGY
REV
VOUT1
E2
__
ECO
C4
22uF
6.3V
1206
C3
22uF
6.3V
1206
R7
49.9K
R3
100K
R1
301K
2
OPTIONAL COMPONENTS
C6
1000pF
R5
100K
L1 4.7uH
L2 1.0uH
C5
1000pF
D2
19
CUSTOMER NOTICE
2
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.
15
VIN
E1
7V -42V
TRANSIENT TO 55V
GND
16
D
4
GND
17
1
2
5
A
B
C
D
DEMO MANUAL DC1727A
Schematic Diagram
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DEMO MANUAL DC1727A
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 application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
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Linear Technology Corporation
LT 0711 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2011
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