1
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 DC2490
A 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 V
OUT
+
and
V
OUT
–
to serve as a minimum load.
The Performance Summary table summarizes the perfor-
mance of the demo board at room temperature. The demo
c
ir
cuit 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 T
A
= 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage 36 48 72 V
Output Voltage I
OUT
= 2.5mA to 0.65A 4.75 5 5.25 V
Maximum Output Current V
IN
= 36V 0.65 A
V
IN
= 48V 0.73 A
V
IN
= 72V 0.84 A
Output Voltage Ripple (Peak to Peak) V
IN
= 48V, I
OUT
= 0.73A 50 mV
Typical Switching Frequency V
IN
= 48V, I
OUT
= 0.73A 260 kHz
Efficiency V
IN
= 36V, I
OUT
= 0.65A 86 %
V
IN
= 48V, I
OUT
= 0.73A 86 %
V
IN
= 72V, I
OUT
= 0.84A 85 %
