DC1619A - Demo Manual

DEMO MANUAL DC1619A
LT3845A: High Voltage
Synchronous Buck Controller
with Programmable
Frequency and Sync
DESCRIPTION
Demonstration Circuit 1619A is a 100kHz to 500kHz
programmable frequency, high voltage, current mode
DC/DC step-down converter featuring the LT®3845A. The
operating frequency can be synchronized up to 600kHz.
This demo board is designed for 12V up to 10A (120W)
output from a 16V to 60V input. A soft-start feature controls
the output voltage slew rate at start-up, reducing current
surges and voltage overshoots. The modes of operation
(Burst Mode®, discontinuous current mode and continuous
current mode) are jumper selectable. Both Burst Mode
operation and discontinuous current mode increase the
efficiency at light loads. Continuous current mode will
maintain a constant switching frequency regardless of
the load current.
output voltages. In such applications, this optional circuit
can increase the overall efficiency by reducing the power
loss in the LT3845A. The demonstration board has the
option of doubling the number of switching MOSFETs to
facilitate higher output current. This board is suitable for
a wide range of industrial control systems and telecom
power supplies.
An optional boost bias circuit is provided on the bottom
side of the board for back-driving the LT3845A internal
regulator from the output voltage. Customers may want
to use this optional circuit with modified applications
that have relatively high input voltages and low (~3.3V)
Design files for this circuit board are available at
http://www.linear.com/demo
PERFORMANCE SUMMARY
PARAMETER FOR BUCK REGULATOR
The LT3845A 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 1619A.
Note: It is best to ground the SYNC pin if the SYNC function is not being 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.
(TA = 25°C)
CONDITION
VALUE
Minimum Input Voltage
16V
Maximum Input Voltage
60V
Output Voltage, VOUT
12V ±2%
Maximum Output Current
VIN < 28V
VIN ≥ 28V
7.5A to 10A (See Figure 5)
10A
Typical Switching Frequency
R9 = 49.9k
300kHz
External Clock Synchronous Frequency Range
R9 = 49.9k
325kHz to 600kHz
Efficiency
VIN = 48V, VOUT = 12V, IOUT = 8A
94% (See Figure 3)
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1
DEMO MANUAL DC1619A
QUICK START PROCEDURE
Demonstration circuit 1619A is easy to set up to evaluate
the performance of the LT3845A. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
4. Turn on the power at the input and adjust the input
voltage until the LT3845A turns on.
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 directly across the VIN or VOUT capacitors by
soldering leads on the appropriate capacitor. See Figure 2
for proper scope probe technique. An oscilloscope probe
can be directly connected to VIN or VOUT using a banana
jack to BNC adaptors.
5. Check for the proper output voltage.
1. Place JP1 in the RUN position.
2. Place JP2 in the desired operating mode: burst, pulseskipping or continuous.
3. With power off, connect the input power supply to VIN
and GND.
–
V
+
Note: Make sure that the input voltage does not exceed 60V.
Note: If output does not come up, make sure the load
is not set too high. Reduce the load and repeat steps
4 and 5.
6. Once the proper output voltage is established, adjust the
input voltage and load within the operating range and
observe the output voltage regulation, ripple voltage,
efficiency and other parameters.
7. An external clock can be added to the SYNC pin when
the SYNC function is used. See the Oscillator SYNC
section in the data sheet for details.
–
–
0V TO 60V
7.5A
+
+
LOAD
0A TO 10A
A
–
–
A
+
+
–
V
+
DC1619 F01
Figure 1. Proper Measurement Equipment Setup
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2
DEMO MANUAL DC1619A
QUICK START PROCEDURE
WIRE
INPUT OR OUTPUT CAPACITOR
Figure 2. Measuring Input or Output Ripple
100
95
EFFICIENCY (%)
90
85
80
75
70
16VIN
20VIN
24VIN
36VIN
48VIN
60VIN
65
60
55
50
0
1
2
3
4
5 6
IOUT (A)
7
8
9
10
DC1619A F03
Figure 3. DC1619A Burst Mode Efficiency
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3
DEMO MANUAL DC1619A
QUICK START PROCEDURE
Figure 4. DC1619A 2A to 8A Load Transient
10.5
IOUT(MAX) (A)
10.0
9.5
9.0
8.5
8.0
7.5
16 20 24 28 32 36 40 44 48 52 56 60
VIN (V)
DC1619A F05
Figure 5. DC1619A Output Current Derating Graph
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DEMO MANUAL DC1619A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
2
CIN1, CIN2
CAP., SMT Aluminum, 33μF, 63V
SUNCON, 63HVH33M
2
2
CIN3, CIN4
CAP., X7R, 2.2μF, 100V, 10%, 1210
MURATA,GRM32ER72A225KA35L
3
1
COUT1
CAP., POSCAP, 68μF, 16V, 20%,
SANYO, 16TQC68M
4
1
COUT3
CAP., X5R, 22μF, 16V, 10%, 1210
TAIYO, EMK325BJ226KM-T
5
1
C1
CAP., X5R, 0.47μF, 100V, 10%, 1206
TDK, C3216X5R2A474KAT
6
2
C2, C5
CAP., X7R, 1500pF, 50V, 10%, 0402
AVX, 04025C152KAT
7
1
C4
CAP., C0G, 100pF, 50V, 10%, 0402
TDK, C1005COG1H101J
8
1
C6
CAP., X5R, 0.1μF, 16V, 10%, 0402
AVX, 0402YD104KAT
9
1
C7
CAP., X5R, 1μF, 16V, 10%, 0603
TDK, C1608X5R1C105K
10
1
C9
CAP., C0G, 220pF, 100V, 10%, 1206
VISHAY, VJ1206A221XB
11
1
D1
HIGH VOLTAGE SWITCHING DIODE, SOD-523
PHILLIPS, BAS521
12
1
D2
SMT SCHOTTKY BARRIER RECTIFIER, SMB
DIODES INC, B160-13-F
13
1
D3
HIGH VOLTAGE SWITCHING DIODE, SOD-323
DIODES INC, 1N4148WS-7-F
14
1
L1
INDUCTOR, 10μH
WURTH ELEKTRONIC, 74435561100
15
2
Q1, Q2
N-MOSFET, 80V
INFINEON, BSC123N08NS3
16
1
R1
RES., CHIP, 1M, 1/16W, 1%, 0402
VISHAY, CRCW04021M00FKED
17
1
R2
RES., CHIP, 97.6k, 1/16W, 1%, 0402
VISHAY, CRW040297K6FKED
18
1
R4
RES., CHIP, 143k, 1/16W, 1%, 0402
VISHAY, CRCW0402143KFKED
19
1
R5
RES., CHIP, 16.2k, 1/16W, 1%, 0402
VISHAY,CRCW040216K2FKED
20
1
R7
RES., CHIP, 20k, 1/16W, 1%, 0402
VISHAY, CRCW040220K0FKED
21
1
R9
RES., CHIP, 49.9k, 1/16W, 1%, 0402
VISHAY,CRCW040249K9FKED
22
1
R10
RES., CHIP, 4.99Ω, 1/16W, 1%, 0402
VISHAY,CRCW04024R99FKED
23
1
R16
RES., CHIP, 6.65Ω, 1/4W, 1%, 1206
VISHAY, CRCW12066R65FKED
24
1
R17
RES., CHIP, 0.007Ω, 1W, 1%, 2512
VISHAY, WSL25127L000FEA
25
1
U1
I.C, LT3845AEFE#PBF, TSSOP (4.4MM) 16-PIN
LINEAR TECH., LT3845AEFE#PBF
Additional Demo Board Circuit Components
1
0
COUT2 (OPT)
CAP., POSCAP, 68μF, 16V, 20%,
SANYO, 16TQC68M
2
0
COUT4 (OPT)
CAP., X5R, 22μF, 16V, 10%, 1210
AVX, 1210YD226KAT
3
0
C3, C8, C10-C13 (OPT)
CAP., 0402
4
0
D4, D5 (OPT)
DUAL SMT SWITCHING DIODE, SOT-23
DIODES INC, BAV99-7-F
5
1
R3
RES., CHIP, 5.1M, 1/16W, 5%, 0402
PANASONIC, ERJ2GEJ515X
6
5
R11-R15
RES., CHIP, 0Ω, 1/16W, 0402
VISHAY, CRCW04020000Z0ED
7
1
R8
RES., CHIP, 100k, 1/16W, 1%, 0402
VISHAY, CRCW0402100KFKED
8
0
Q4, Q5 (OPT)
N-MOSFET, 80V
INFINEON, BSC123N08NS3
9
0
Q3 (OPT)
COMPLIMENARY MOSFET PAIR, SC-70
VISHAY, Si1555DL-T1-E3
10
0
R6, R18-R22 (OPT)
RES., 0402
Hardware For Demo Board Only
1
4
J1-J4
JACK, BANANA
KEYSTONE, 575-4
2
5
E1-E5
TESTPOINT, TURRET, 0.095"
MILL-MAX, 2501-2-00-80-00-00-07-0
3
1
JP1
JMP, 3-PIN 1 ROW 0.079CC
SAMTEC, TMM-103-02-L-S
4
1
JP2
2MM DOUBLE ROW HEADER 2x3
SAMTEC, TMM-103-02-L-D
5
2
JP1(1 and 2), JP2 (5 and 6)
SHUNT, 0.079" CENTER
SAMTEC, 2SN-BK-G
6
4
STAND-OFF
STAND-OFF, NYLON 0.50" tall
KEYSTONE, 8833(SNAP ON)
dc1619af
5
B
A
E2
J1
J2
SYNC
E3
6 BURST
5
CIN2
33uF
63V*
CIN3
2.2uF
100V
1210
R3
5.1M
5%
R6
R5
16.2K
1%
R4
1%
(OPT)
VFB
* 79V CAPACITOR SURGE VOLTAGE
CIN1 +
33uF
63V*
PULSE SKIP
4
3
VFB
2
1
CONT .
+
VCC
JP2
MODE
GND
GND
VIN
16V - 60V
E1
143K
(OPT)
C3
SHDN
RUN
CIN4
2.2uF
100V
1210
R7
20K
1
R8
100K
U1
8 FSET
7 SYNC
6 VC
5 VFB
4 BURST_EN
3 SS
2 SHDN
1 VIN
R9
49.9K
1500pF
C2
100V
1206
C1
0.47uF
C4
100pF
R2
97.6K
C5
1500pF
2
JP1
R1
1M
LT3845AEFE
17 SGND
VIN
1
3
SENSE- 9
SENSE+ 10
PGND 11
BG 12
VCC 13
SW 14
TG 15
BOOST 16
0
R11
TG
4.99
R10
D3
1N4148
0
C8
(OPT)
R13
16V
BG
VCC
D1
BAS521
R12
C6
0.1uF
0
4
VCC
C7
1uF
16V
0603 BG
TG
4
8
7
6
5
1
2
3
8
7
6
5
6
R15
R14
1
2
3
1
0
0
C9
220pF
100V
1206
R16
6.65
1206
L1
D2
B160
10uH*
VS+
0.007
2512
R17
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
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.
CUSTOMER NOTICE
2
+
2
-
COUT1 +
68uF
16V
REV
ECO
DESCRIPTION
DATE
GND
GND
VOUT
12V, 120W
VOUT
11-15-10
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
E5
J3
J4
E4
VOUT
MARTY M.
APPROVED
DATE:
N/A
SIZE
11-15-10
IC NO.
LT3845AEFE
DEMO CIRCUIT 1619A
SHEET 1
OF
2
2
REV.
HIGH VOLTAGE SYNCHRONOUS BUCK
CONTROLLER WITH ADJUSTABLE OPERATING FREQUENCY
TECHNOLOGY
COUT3
22uF
16V
1210
VOUT
COUT4
(OPT)
1210
REVISION HISTORY
PRODUCTION FAB
COUT2
(OPT)
NC
MARTY M. TITLE: SCHEMATIC
SCALE = NONE
APP ENG.
PCB DES.
APPROVALS
* L1 LAYOUT PADS ARE NON-STANDARD PADS DESIGNED TO
ACCOMMODATE THE WURTH ELEKTRONIC, 74435561100 INDUCTOR
OR THE WURTH ELEKTRONIC, 7443551151 INDUCTOR
NOTES:UNLESS OTHERWISE SPECIFIED
RESISTORS: OHMS, 0402
CAPACITORS: uF, 0402
Q2
BSC123N08N
SW
Q1
BSC123N08N
VIN
2
B
A
DEMO MANUAL DC1619A
SCHEMATIC DIAGRAM
dc1619af
B
A
C10
1uF
10V
R18
2
D4
BAV99
C11
1uF
10V
1
2VOUT
3VOUT
C12
1uF
10V
2
R19
D5
BAV99
1
C13
1
REFER TO THE LT3845AEFE DATASHEET FOR MORE DETAILS.
USE OPTIONAL BIAS CIRCUIT TO BACKFEED VCC WHEN VOUT IS BETWEEN
3V AND 9V AND VCC POWER DISSIPATION EXCEEDS 250mW.
VCC
3
1uF
10V
OPTIONAL BIAS CIRCUIT
3
4
3
6
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.
2
R20
BG
CUSTOMER NOTICE
Q3A
Si1555DL
5
Q3B
Si1555DL
VOUT
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
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.
1
MARTY M. TITLE: SCHEMATIC
TECHNOLOGY
4
4
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
Q5
Q4
IC NO.
2
DATE: 11-15-10
N/A
SIZE
LT3845AEFE
DEMO CIRCUIT 1619A
SHEET 2
OF
2
2
REV.
HIGH VOLTAGE SYNCHRONOUS BUCK
CONTROLLER WITH ADJUSTABLE OPERATING FREQUENCY
NC
PCB DES.
SCALE = NONE
R21
R22
APP ENG.
APPROVALS
BG
SW
TG
VIN
OPTIONAL POWER FETS
2
8
7
6
5
1
2
3
8
7
6
5
1
2
3
1
B
A
DEMO MANUAL DC1619A
SCHEMATIC DIAGRAM
dc1619af
7
DEMO MANUAL DC1619A
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
dc1619af
8
Linear Technology Corporation
LT 0211 • 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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