HCPL-800J Datasheet, PDF (18/18 Pages) AVAGO TECHNOLOGIES LIMITED – Under-Voltage Detection

5V
100 nF
78L05
VOUT
VIN
GND
1000 µF
9.1 V 1 W
GND2
Figure 30. A simple low cost non-isolated power supply
+
C* 470 µH 120 mA
630 mA
L
X2 1.5 µF/3.3 µF
-
VARISTOR
220 kÙ
N
* 1.5µF X2 for 230V mains, 3.3µF X2 for 110V mains
VCC2 Power Supply Requirements
The recommended voltage regulator to supply V_CC2 is
a low cost 78L05 or equivalent. To minimize harmonic
distortion, it is recommended to connect a tantalum
decoupling capacitor of at least 10 µF together with
a 100 nF ceramic capacitor in parallel. The capacitors
should be positioned as close as possible to the supply
input pin. The supply voltage for the regulator can be
supplied from the system level power supply transform-
er (powerline side winding). Alternatively, the supply can
be derived directly from the powerline via a simple low
cost circuit as shown in Figure 30.
Thermal Considerations
The high efficiency line driver used in the HCPL-800J
ensures minimum internal power dissipation, even for
high peak output currents. Despite this, operating the
line driver continuously with high output currents at
elevated ambient temperatures can cause the peak
junction temperature to exceed 125°C and/or resulting
in the triggering of the thermal protection.
To prevent this from happening, when operating the
line driver continuously with high output currents,
an ambient temperature derating factor needs to be
applied. A typical derating curve is shown in Figure 31.
In this case the assumption is that the transmitter is
operating continuously in still air with a typical 2-layer
Printed-Circuit Board (PCB). However, it should be noted
that operating the transmitter discontinuously for short
periods of time will allow lower derating or even no
derating at all. Conversely operating the line driver con-
tinuously with a poor PCB layout and/or with restricted
air convection could result in the requirement for a larger
derating factor.
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-40
-15
10
35
60
85
T_A – AMBIENT TEMPERATURE – °C
Figure 31. Power derating vs. temperature
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Data subject to change. Copyright © 2005-2009 Avago Technologies. All rights reserved. Obsoletes 5989-0402EN
AV02-0413EN - August 28, 2009