Application Information
Bypassing and PC Board Layout
to be connected directly to the
inputs and outputs.
As shown in Figure 6, the only
external component required for
proper operation is the bypass
capacitor. Capacitor values
should be between 0.01
µF
and
The HCPL-0708 optocoupler is
extremely easy to use. No
external interface circuitry is
required because the HCPL-0708
uses high-speed CMOS IC
technology allowing CMOS logic
0.1
µF.
For each capacitor, the
total lead length between both
ends of the capacitor and the
power-supply pins should not
exceed 20 mm. Figure 7
illustrates the recommended
printed circuit board layout for
the HPCL-0708.
1
V
I
2
3
4
8
C
7 NC
6
5
GND
XXX
YWW
V
DD
V
O
C1, C2 = 0.01 µF TO 0.1 µF
Figure 6. Recommended printed circuit board layout.
V
DD
V
I
Figure 7. Recommended printed circuit board layout.
Propagation Delay, Pulse-Width
Distortion and Propagation Delay
Skew
Propagation Delay is a figure of
merit which describes how
quickly a logic signal propagates
through a system. The propaga-
XXX
YWW
C2
V
O
GND
C1, C2 = 0.01 µF TO 0.1 µF
tion delay from low to high (t
PLH
)
is the amount of time required for
an input signal to propagate to
the output, causing the output to
change from low to high.
Similarly, the propagation delay
from high to low (t
PHL
) is the
amount of time required for the
input signal to propagate to the
output, causing the output to
change from high to low. See
Figure 8.
INPUT
V
I
t
PLH
OUTPUT
V
O
90%
10%
t
PHL
90%
5 V CMOS
50%
0V
10%
V
OH
2.5 V CMOS
V
OL
Figure 8.
8
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