HCPL-0710500 Agilent(Hewlett-Packard), HCPL-0710500 Datasheet - Page 8

• Manufacturer Part Number: HCPL-0710500
• Description: 40 ns Prop. Delay/ SO-8 Optocoupler
• Manufacturer: Agilent(Hewlett-Packard)

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-
Pulse-width distortion (PWD) is
the difference between t
t
maximum 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 trans-
mitted. Typically, PWD on the
order of 20 - 30% of the minimum
pulse width is tolerable. The PWD
specification for the HCPL-0710
is 8 ns (10%) maximum across
recommended operating condi-
tions. 10% maximum is dictated
by the most stringent of the three
fieldbus standards, PROFIBUS.
Propagation delay skew, t
an important parameter to con-
sider in parallel data applications
where synchronization of signals
Figure 13.
INPUT
OUTPUT
PLH
V
V
and often determines the
O
I
10%
90%
t
PLH
PHL
PSK
and
, is
t
PHL
90%
tion delay from low to high (t
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
50%
on parallel data lines is a concern.
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 the optocouplers at
different times. If this difference
in propagation delay is large
enough it will determine the
maximum rate at which parallel
data can be sent through the
optocouplers.
Propagation delay skew is defined
as the difference between the
minimum and maximum propa-
gation delays, either t
for any given group of optocoup-
lers which are operating under
the same conditions (i.e., the
same drive current, supply volt-
age, output load, and operating
10%
5 V CMOS
0 V
V
2.5 V CMOS
V
OH
OL
PHL
PLH
) is the
or t
PHL
PLH
,
)
amount of time required for the
input signal to propagate to the
output, causing the output to
change from high to low. See
Figure 13.
temperature). As illustrated in
Figure 14, if the inputs of a group
of optocouplers are switched
either ON or OFF at the same
time, t
between the shortest propagation
delay, either t
longest propagation delay, either
t
As mentioned earlier, t
determine the maximum parallel
data transmission rate. Figure 15
is the timing diagram of a typical
parallel data application with both
the clock and data lines being
sent through the optocouplers.
The figure shows data and clock
signals at the inputs and outputs
of the optocouplers. In this case
the data is assumed to be clocked
off of the rising edge of the clock.
PLH
or t
PSK
PHL
is the difference
.
PLH
or t
PHL
PSK
, and the
can