Linear Technology DC2490A Quick setup guide
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dc2490af
DEMO MANUAL DC2490A
Description
LT8303
Micropower No-Opto
Isolated Flyback Converter
Demonstration circuit 2490A is a micropower no-opto
isolated flyback converter featuring the LT
®
8303. This
demo circuit outputs 5V, and maintains tight regulation
with a load current from 2.5mA to 0.84A over an input
voltage from 36V to 72V. The output current capabil-
ity increases with the input voltage, as shown in the
Performance Summary table.
The DC2490A needs less than 0.5% of its full output
power as a minimum load to maintain good output voltage
regulation. On the DC2490A, in order to avoid preload-
ing, a 5.6V Zener diode is placed between its VOUT+and
VOUT–to serve as a minimum load.
The Performance Summary table summarizes the perfor-
mance of the demo board at room temperature. The demo
circuit can be easily modified for different applications with
some predesigned transformers.
The LT8303 is a micropower high voltage isolated fly-
back converter. By sampling the isolated output voltage
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
performance summary
directly from the primary-side flyback waveform, the part
requires no third winding or opto-isolator for regulation.
The output voltage is programmed with a single external
resistor. Boundary mode operation provides a small mag-
netic solution with excellent load regulation. Low ripple
Burst Mode
®
operation maintains high efficiency at light
load while minimizing the output voltage ripple. A 0.45A,
150V DMOS power switch is integrated along with all
the high voltage circuitry and control logic into a 5-lead
ThinSOT™ package.
The LT8303 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 2490A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2490A
Specifications are at TA= 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage 36 48 72 V
Output Voltage IOUT = 2.5mA to 0.65A 4.75 5 5.25 V
Maximum Output Current VIN = 36V 0.65 A
VIN = 48V 0.73 A
VIN = 72V 0.84 A
Output Voltage Ripple (Peak to Peak) VIN = 48V, IOUT = 0.73A 50 mV
Typical Switching Frequency VIN = 48V, IOUT = 0.73A 260 kHz
Efficiency VIN = 36V, IOUT = 0.65A 86 %
VIN = 48V, IOUT = 0.73A 86 %
VIN = 72V, IOUT = 0.84A 85 %
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dc2490af
DEMO MANUAL DC2490A
Quick start proceDure
Demonstration circuit 2490A is easy to set up to evalu-
ate the performance of the LT8303. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
1. With power off, connect the input power supply to the
board through VIN (E1) and GND (E2) terminals. Con-
nect the load to the terminals VOUT+(E3) and VOUT–(E4)
on the board.
2.Turnonthepowerattheinput.IncreaseVIN slowlyto36V.
NOTE: Make sure that the input voltage is always within
spec. To operate the board with higher input/output
voltage, input capacitor, output capacitor and output
diode with higher voltage ratings are needed.
3. Check for the proper output voltages. The output should
be regulated at 5V (±5%).
NOTE: The LT8303 requires very small minimum load
to maintain good output voltage regulation. A Zener
diode is placed on the output to clamp the voltage to
5.6V. This Zener can be replaced with a 2000Ω resistor
at the trade-off of lower efficiency.
4. Once the proper output voltage is established, adjust
the input voltage and load current within the operating
range and observe the output voltage regulation, ripple
voltage, efficiency and other parameters.
NOTE: When measuring the input or output voltage
ripples, 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 (E1) and GND (E2), or VOUT+(E3) and
VOUT–(E4) terminals. See Figure 2 for proper scope
probe technique.
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DEMO MANUAL DC2490A
Quick start proceDure
Figure 1. Proper Measurement Equipment Setup
Figure 2. Proper Scope Probe Placement for Measuring Input or Output Ripple
Figure 3. Efficiency vs Load Current Figure 4. Load and Line Regulation
INPUT OR OUTPUT CAPACITOR
VIN = 36V
VIN = 48V
VIN = 72V
LOAD CURRENT (mA)
0
100
200
300
400
500
600
700
800
900
40
50
60
70
80
90
100
EFFICIENCY (%)
DC2490a F03
V
IN
= 36V
V
IN
= 48V
V
IN
= 72V
LOAD CURRENT (mA)
0
100
200
300
400
500
600
700
800
900
4.9
5.0
5.1
5.2
OUTPUT VOLTAGE (V)
DC2490a F04
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DEMO MANUAL DC2490A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C1 CAP, 4.7µF, X7S, 100V, 10% 1210 MURATA, GRJ32DC72A475KE11L
2 1 C2 CAP, 220µF, X5R, 6.3V, 20% 1210 SAMSUNG, CL32A227MQVNNNE
3 1 D1 DIODE, SCHOTTKY, 30V, 3A, PowerDI123 DIODES INC, SBR3U30P1-7
4 1 D2 DIODE, ZENER, 5.6V, 300mW, SOD-523 DIODES INC, BZT52C5V6T-7
5 1 D3 DIODE, ZENER, 62V, SOD-123 CENTRAL SEMI, CMHZ5265B
6 1 D4 DIODE, 200V, SOD-123 CENTRAL SEMI, CMMR1U-02
7 1 R1 RES, 402k, 1/10W, 1%, 0603 VISHAY, CRCW0603402KFKEA
8 1 R2 RES, 15.4k, 1/10W, 1% 0603 VISHAY, CRCW060315K4FKEA
9 1 R3 RES, 316k, 1/10W, 1%, 0603 VISHAY, CRCW0603316KFKEA
10 1 T1 TRANSFORMER, PS15-109 SUMIDA, PS15-109
11 1 U1 IC, LT8303ES5#PBF, TSOT23-5 LINEAR TECHNOLOGY, LT8303ES5#PBF
Additional Demo Board Circuit Components
1 0 C3 (OPT) CAP, OPT, 1210
2 0 C4 (OPT) CAP, OPT, 1808
3 0 CIN (OPT) CAP, 10µF, ALUM, 80V
Hardware: For Demo Board Only
1 4 E1 TO E4 TESTPOINT, TURRET, 0.094" PBF MILL-MAX, 2501-2-00-80-00-00-07-0
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DEMO MANUAL DC2490A
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
VIN
GND
36V - 72V
NOTE: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS AND CAPACITORS ARE 0603.
SEE DEMO MANUAL
*
5.6V
+5V
*
D2
BZT52C5V6T-7
OPT
C3
1210
T1
PS15-109
1
3
4
6
5E4
VOUT-
+
CIN
OPT
R2
15.4K
E1
R3 316K
R1
402K
D1
SBR3U30P1-7
D4
CMMR1U-02
E2
E3
VOUT+
OPTC4
1808
4.7uF
100V
C1
1210
220uF
C2
6.3V
1210
D3
CMHZ5265B
U1
LT8303ES5
VIN 5
EN/UV
1
RFB
3
GND
2
SW 4
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DEMO MANUAL DC2490A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ●FAX: (408) 434-0507 ●www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2016
LT 0716 • 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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