Linear Technology LT8494 Quick setup guide
1
dc2242af
DEMO MANUAL DC2242A
Description
LT8494
SEPIC/Boost DC/DC Converter with 2A,
70V Switch, and 7µA Quiescent Current
Demonstration circuit 2242A is a monolithic SEPIC con-
verter featuring LT
®
8494.The demo board is designed for
5V output from a 3V to 60V input at 450kHz switching
frequency. The max output current is 1A when the input
voltage is above 12V, and is reduced with lower input volt-
age.ThequiescentcurrentofLT8494islessthan7μA when
operating. Dual supply pins (VIN and BIAS)allow the part
to automatically operate from the most efficient supply.
Low ripple Burst Mode
®
operation increases the efficiency
at the light load while keeping the output ripple below
10mV. Figure 1shows the demo board efficiency at 12V
input voltage.Figure 2shows the maximum load current
with different input voltages of the demo board.
L,LT ,LT C ,LT M ,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.
performance summary
The LT8494 data sheet gives a complete description of the
part,operation and application information.The data sheet
must be read in conjunction with this demo manual for
DC2242A. The LT8494 is assembled in 20-lead QFN and
20-lead plastic TSSOP packages.Proper board layout is
essentialformaximumthermalandelectricalperformance.
See the data sheet sections for details.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2242A
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Supply Range 3 60 V
VOUT Output Voltage 4.86 5.04 5.24 V
fSW Switching Frequency RT= 169kΩ 414 450 477 kHz
IOUT Max Output Current VIN = 12V 1 A
EFE Efficiency at DC VIN = 12V, IOUT = 1A 80.3 %
LOAD CURRENT (A)
40
EFFICIENCY (%)
60
90
50
70
80
0.4
DC2242A F01
10.20 0.6 0.8
VIN = 12V
VOUT = 5V
fSW = 450kHz
INPUT VOLTAGE (V)
0
MAXIMUM LOAD CURRENT (A)
1.0
2.5
0.5
1.5
2.0
20
DC2242A F01
60100 30 5040
Figure 1. LT8494 Efficiency Figure 2. LT8494 Maximum Load Current
(Typical) vs Input Voltage
2
dc2242af
DEMO MANUAL DC2242A
Quick start proceDure
DC2242A is easy to set up to evaluate the performance
of the LT8494. Refer to Figure 3for 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 4for the proper
scope technique.
1. With power off,connect the input power supply to VIN
and GND.Make sure that the input voltage does not
exceed 60V.
2. With power off, connect loads from VOUT to GND.
3. Turn on the power at the input.
4. Check for the proper output voltages (VOUT = 5V).
NOTE: If there is no output,temporarily disconnect the
load to make sure that the load is not set too high or
is shorted.
5. Once the proper output voltage is established,adjust
the load within the operating ranges and observe the
output voltage regulation,ripple voltage,efficiency and
other parameters.
3
dc2242af
DEMO MANUAL DC2242A
Quick start proceDure
Figure 3. Proper Measurement Equipment Setup
V
OUT
GND
Figure 4. Measuring Input or Output Ripple
4
dc2242af
DEMO MANUAL DC2242A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C2, C8 CAP., X7R, 2.2µF, 100V, 10%, 1210 MURATA, GRM32ER72A225KA35L
2 2 C3, C4 CAP., X7R, 47µF, 10V, 10%, 1210 MURATA, GRM32ER71A476KE15L
3 2 C5, C7 CAP., X7R, 1µF, 10V, 10%, 0603 MURATA, GRM188R71A105KA61D
4 1 C6 CAP., NP0, 4.7pF, 50V, ±0.25pF, 0603 MURATA, GRM1885C1H4R7CA01D
5 1 D1 DIODE, SCHOTTKY 100V, 2A, SMA ON SEMI., MBRA2H100T3G
6 1 L1 INDUCTOR, 15µH VISHAY, IHCL4040DZER150M5A
7 2 R1, R10 RES., CHIP, 1M, 1/10W, 0603 VISHAY, CRCW06031M00FKEA
8 1 R2 RES., CHIP, 316K, 1/10W, 1%, 0603 VISHAY, CRCW0603316KFKEA
9 1 R4 RES., CHIP, 100k, 1/10W, 1%, 0603 VISHAY, CRCW0603100KFKEA
10 1 R6 RES., CHIP, 169k, 1/10W, 1%, 0603 VISHAY, CRCW0603169KFKEA
11 1 R9 RES., CHIP, 0, 1/10W, 0603 VISHAY, CRCW06030000Z0EA
12 1 U1 I.C., , LT8494, TSSOP-20-4.4mm LINEAR TECH., LT8494EFE#PBF
Additional Demo Board Circuit Components
1 1 C1 CAP., ALUM, 10µF, 63V, 20% SUN ELECTRONIC, 63CE10BS
2 0 C10 (OPT) CAP., OPTION, 0603 OPT
3 0 R11 (OPT) RES., OPTION, 0603 OPT
Hardware: For Demo Board Only
1 6 E1-E6 TESTPOINT, TURRET, .094" PBF MILL-MAX, 2501-2-00-80-00-00-07-0
5
dc2242af
DEMO MANUAL DC2242A
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
ALL CAPACITORS ARE IN MICROFARADS, 0603.
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS ARE IN OHMS, 0603.
(450kHz)
100V
*
THE MAX LOAD CURRENT IS REDUCED WHEN THE
INPUT VOLTAGE IS LESS THAN 12V. PLEASE SEE
DEMO MANUAL FOR DETAILS.
*
*
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 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.
www.linear.com
1
DEMO CIRCUIT 2242A
Tuesday, May 05, 2015 11
SEPIC CONVERTER WITH LOW IQ
N/A
LT8494EFE
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 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.
www.linear.com
1
DEMO CIRCUIT 2242A
Tuesday, May 05, 2015 11
SEPIC CONVERTER WITH LOW IQ
N/A
LT8494EFE
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 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.
www.linear.com
1
DEMO CIRCUIT 2242A
Tuesday, May 05, 2015 11
SEPIC CONVERTER WITH LOW IQ
N/A
LT8494EFE
R10
1M
E1
VIN
3V - 60V
C5
1uF
0603
10V
R11
OPT
E2
GND
C8
2.2uF
1210
E6
SWEN
D1
MBRA2H100T3G
C7
1uF E5 PG
R4
100K
1%
C2
2.2uF
100V
1210
C4
47uF
1210
10V
E4 GND
C10
OPT
+
C1
10uF
63V
63CE10BS
LT8494EFE
U1
SS
8
RT
10
NC 11
SWEN
12
NC 13
NC 15
VIN
18
GND
16
GND
14
SW 20
BIAS 1
FB 3
NC
5
NC
6
PG 7
NC
17
FB 2
NC
4
NC
9
NC
19
GND
21
E3 VOUT
5V / 1A
R9
0
C3
47uF
10V
1210
R6
169K
R1
1M
1%
R2
316K
1%
C6
4.7pF
L1
15uH
IHCL4040DZ-5A
42
1 3
6
dc2242af
DEMO MANUAL DC2242A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ●FAX: (408) 434-0507 ●www.linear.com
LINEAR TECHNOLOGY CORPORATION 2015
LT 0715 • 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 application
engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
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