DC1854A - Demo Manual

DEMO MANUAL DC1854A
LT8471EFE
Dual Output, Buck and
Inverting Converter
Description
DC1854A is a dual output buck and inverting converter.
It provides 5V and –5V power from 6V to 32V input. The
5V output can source up to 1.4A load current and the
–5V output can source up to 800mA load current. See
the load current versus input voltage figures inside this
demo manual for more information. The internal skyhook
supply is used to provide voltage to the internal npn switch
and can be used for various topologies. Although they are
assembled as a single inductor buck and a single inductor
inverting converter on DC1854A, the two DC/DC converters
can be altered for different topologies.
The LT®8471 is a dual PWM DC/DC converter containing
two internal 2A, 50V switches and an additional 500mA
switch to facilitate step-down and inverting conversion.
Each 2A channel can be independently configured as a
buck, boost, SEPIC, flyback or inverting converter. Capable of generating positive and negative outputs from a
single input rail, the LT8471 is ideal for many local power
supply designs.
Performance Summary
PARAMETER
The LT8471 has an adjustable oscillator, set by a resistor
placed from the RT pin to ground. Additionally, the LT8471
can be synchronized to an external clock. The free running
or synchronized switching frequency range of the part
can be set between 100kHz and 2MHz. DC1854A is set at
450kHz. Additional features such as frequency foldback,
soft-start, and power good are integrated.
The LT8471 data sheet gives a complete description of
the part, operation and applications information. The data
sheet must be read in conjunction with this Demo Manual
for DC1854A. The LT8471EFE is assembled in a 20-lead
plastic TSSOP (FE) package with a thermally enhanced
ground pad. Proper board layout is essential for maximum
thermal performance. See the data sheet section Layout
Considerations.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1854A
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.
Specifications are at TA = 25°C
CONDITIONS
MIN
VIN Input Voltage Range
TYP
6 to 32
450
MAX
UNITS
V
Switching Frequency
R1 = 187k
VOUT1
R2 = 316k, R3 = 59k
Maximum Load Current IOUT1
VIN = 6V
VIN = 12V
VIN = 28V
VOUT2
R4 = 316k, R5 = 59k
Maximum Load Current IOUT2
VIN = 6V
VIN = 12V
VIN = 28V
Efficiency
VIN = 12V, IOUT1 = 1.45A, IOUT2 = 840mA
VOUT1 AC ripple
VIN = 12V, IOUT1 = 1.45A
7
mVP-P
VOUT2 AC ripple
VIN = 12V, IOUT2 = 840mA
13
mVP-P
5
1.5
1.45
1.2
kHz
V
A
A
A
–5
550
840
1
V
mA
mA
A
80.6
%
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DEMO MANUAL DC1854A
Quick Start Procedure
DC1854A is easy to set up to evaluate the performance of
the LT8471EFE Follow the procedure below:
3.Connect resistive or electronic loads within the maximum
parameters to outputs VOUT1 and VOUT2.
1.Connect the OV/UV terminal to GND to disable switching
during power supply startup.
4.Release the OV/UV-to-GND connection.
2.With power off, connect the input power supply to the
VIN and GND terminals. Make sure that the VIN DC
input voltage will not exceed 32V.
5.Observe the VOUT1 and VOUT2 voltages as well as the
PG1 and PG2 voltages. Observe the circuit efficiency
or other operation while the input voltage is between
6V and 32V.
Figure 1. Test Procedure Setup Drawing for DC1854A
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DEMO MANUAL DC1854A
90
1.75
85
1.50
75
70
65
1.00
VOUT2 (–5V)
0.75
0.50
60
0.25
55
50
VOUT1 (5V)
1.25
IOUT MAX (A)
EFFICIENCY (%)
80
5
10
15
20
VIN (V)
25
30
35
0
5
10
15
dc1854 F02
Figure 2. DC1854A Efficiency at IOUT1,2 Max
vs VIN (see Figure 3)
20
VIN (V)
25
30
35
dc1854 F03
Figure 3. DC1854A CH1 and CH2 Maximum
Load Current vs Input Voltage
VOUT1
VOUT2
dc1854 F04
Figure 4. DC1854A Output Voltage Ripple 12VIN, IOUT1 = 1.45A, IOUT2 = 840mA (Bandwidth Limit Enabled)
Figure 5. DC1854A Output Voltage Ripple Measurement Method
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DEMO MANUAL DC1854A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
2
C1, C2
CAP., X7R 0.47µF 50V 10% 1206
MURATA, GRM31MR71H474KA01L
2
3
C3, C4, C5
CAP., X5R 2.2µF 50V 10% 1206
MURATA, GRM31CR61H225KA88L
3
1
C6
CAP., X5R 1µF 50V 10% 1206
TDK, C3216X5R1H105K 2 rls
4
2
C7, C8
CAP., X7R 0.1µF 16V 10% 0603
MURATA, GRM188R71C104KA01D
5
4
C9, C10, C14, C17
CAP., X5R 47µF 10V 10% 1210
MURATA, GRM32ER61A476KE20L
6
1
D1
DIODE, SCHOTTKY 40V 2A POWERDI123
DIODES INC., DFLS240L-7
7
1
D2
DIODE, SCHOTTKY 60V 2.1A DO214AC
VISHAY, VS-10MQ060NTRPBF
8
1
L1
INDUCTOR, 6.8µH 4020
WURTH ELECTRONIK, 74437324068
9
1
L2
INDUCTOR, 10µH 4020
WURTH ELECTRONIK, 74437324100
10
1
L3
INDUCTOR, 15µH ±20%
WURTH ELECTRONIK, 744025150
11
1
R1
RES., CHIP 187k 0.1W 1% 0603
VISHAY, CRCW0603187KFKEA
12
2
R2, R4
RES., CHIP 316k 0.1W 1% 0603
VISHAY, CRCW0603316KFKEA
13
2
R3, R5
RES., CHIP 59k 0.1W 1% 0603
VISHAY, CRCW060359K0FKEA
14
1
U1
I.C., VOLTAGE REG. TSSOP20-FE/CB
LINEAR TECH., LT8471EFE#PBF
Additional Demo Board Circuit Components
1
0
C11, C12, C15, C16, C18, C19 (Opt)
CAP., 1210
2
1
C13
CAP., ALUM 47µF 35V 10%
3
0
C20
CAP., 1206
4
0
C21, C22
CAP., 0603
5
0
D3
SCHOTTKY DIODE SOD-123
SUN ELECT., 35CE47AX
6
1
R6
RES., CHIP 499k 0.1W 1% 0603
7
0
R7, R11, R12
RES., 0603
VISHAY, CRCW0603499KFKEA
8
2
R8, R9
RES., CHIP 100k 0.1W 5% 0603
VISHAY, CRCW0603100KFKEA
9
1
R10
RES/JUMPER, CHIP 0Ω 0.25W 5A 0603
VISHAY, CRCW06030000Z0EA
Hardware: For Demo Board Only
1
13
E1-E13
TURRET, TESTPOINT
MILL MAX, 2501-2-00-80-00-00-07-0
2
4
MH1-MH4
STAND-OFF, NYLON 0.25" TALL
KEYSTONE, 8831 (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
D
SS2
SS1
PG2
PG1
E13
E2
E1
SYNC
OV/UV
GND
VIN
6V to 32V
5
E9
E12
R9
100k
R6
499k
1%
C7
0.1µF
0603
15µH
744025150
SS1
PG2
PG1
OV/UV
C3
SHOUT
C8
0.1µF
0603
8
17
4
6
D3
(Opt)
SOD‐123
13
14
ALL RESISTORS 0603.
R7
(Opt)
C6
1µF
50V
1206
L3
C5
2.2µF
50V
1206
C1
0.47µF
50V
1206
C2
0.47µF
50V
1206
3
4
C3
U1
LT8471EFE
FB1
R1
187k
1%
450kHz
3
E1
FB2
E2
2.2µF
50V
1206
NOTE: UNLESS OTHERWISE SPECIFIED.
R11
(Opt)
R8
100k
C20
(Opt)
1206
R10
0 Ohm
C13
47µF
35V
R12
(Opt)
E5
E11
E4
+
15
4
3
VIN1
18
SYNC
9
SS2
VIN2
1
C1
20
C2
7
RT
10
11 GND
12 GND
21 GND
GND
5
5
2
16
19
D1
DFLS240L‐7
6.8µH
74437324068
L1
L2
10µH
74437324100
D2
VS‐10MQ060NTRPBF
C4
2.2µF
50V
1206
R3
59.0k
1%
R2
316k
1%
2
C21
(Opt)
0603
C22
(Opt)
0603
C12
(Opt)
1210
R5
59.0k
1%
R4
316k
1%
C11
(Opt)
1210
2
C10
47µF
10V
1210
C9
47µF
10V
1210
C14
47µF
10V
1210
C17
47µF
10V
1210
C15
(Opt)
1210
C18
(Opt)
1210
1
SGND
C16
(Opt)
1210
C19
(Opt)
1210
E10
E6
E3
E8
E7
*
GND
VOUT1
+5V
1.4A
GND
VOUT2
‐ 5V ‐800mA
*See Demo Manual
1
*
A
B
C
D
DEMO MANUAL DC1854A
Schematic Diagram
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DEMO MANUAL DC1854A
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 0214 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
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