HCPL-0738 データシートの表示（PDF） - HP => Agilent Technologies
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HCPL-0738 Datasheet PDF : 8 Pages
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Application Information
Bypassing and PC Board Layout
The HCPL-0738 optocoupler is
extremely easy to use. No exter-
nal interface circuitry is required
because the HCPL-0738 uses
high-speed CMOS IC technology
allowing CMOS logic to be con-
nected 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
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.
VI1
1
GND 1
2
GND 1
3
VI2
4
8
VDD
C
7
VO 1
6
VO 2
5
GND 2
Figure 6. 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-
tion delay from low to high (tPLH)
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 (tPHL) 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 7).
Pulse-width distortion (PWD)
results when tPLH and tPHL differ
in value. PWD is defined as the
difference between tPLH and tPHL
and often determines the maxi-
mum data rate capability of a
transmission system. PWD can
be expressed in percent by
dividing the PWD (in ns) by the
minimum pulse width (in ns)
being transmitted. Typically,
PWD on the order of 20-30% of
the minimum pulse width is
tolerable; the exact figure de-
pends on the particular applica-
tion (RS232, RS422, T-1, etc.).
Propagation delay skew, tPSK, is
an important parameter to con-
sider in parallel data applications
where synchronization of signals
on parallel data lines is a con-
cern. If the parallel data is being
sent through a group of
optocouplers, differences in
propagation delays will cause the
data to arrive at the outputs of
6
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