ACPL-061L-000E Avago Technologies US Inc., ACPL-061L-000E Datasheet - Page 12

• Manufacturer Part Number: ACPL-061L-000E
• Manufacturer: Avago Technologies US Inc.

Specifications of ACPL-061L-000E

• Number Of Elements: 1
• Input Type: DC
• Output Type: Totem Pole
• Forward Voltage: 1.7V
• Forward Current: 8mA
• Output Current: 10mA
• Isolation Voltage: 3750Vrms
• Operating Temp Range: -40C to 105C
• Pin Count: 8
• Mounting: Surface Mount
• Reverse Breakdown Voltage: 5V
• Operating Temperature Classification: Industrial
• Lead Free Status / Rohs Status: Compliant

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
propagation delay from low-to-high (t
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
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 9).
Pulse-width distortion (PWD) results when t
differ in value. PWD is defined as the difference between
t
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, a PWD of 20-30% of
the minimum pulse width is tolerable; the exact figure
depends on the particular application (RS232, RS422,
T-1, etc.).
Propagation delay skew, t
to consider in parallel data applications where synchroni-
zation of signals on parallel data lines is a concern.
If the parallel data is being sent through a group of opto-
couplers, differences in propagation delays will cause
the data to arrive at the outputs of the optocouplers at
different times. If this difference in propagation delays 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 propagation
delays, either t
couplers which are operating under the same conditions
(i.e., the same supply voltage, output load, and operating
temperature). As shown in Figure 10, if the inputs of a
Figure 9. Propagation delay skew waveform
12
V
V
V
V
PLH
O
O
I
I
and t
PHL.
PWD determines the maximum data rate of
PLH
50%
50%
or t
2.5 V,
CMOS
PHL
, for any given group of opto-
PSK
, is an important parameter
t
PSK
PLH
2.5 V,
CMOS
) is the amount
PLH
and t
PHL
PHL
)
INPUTS
OUTPUTS
group of optocouplers are switched either ON or OFF at
the same time, t
propagation delay, either t
propagation delay, either t
earlier, t
transmission rate.
Figure 10 is the timing diagram of a typical parallel data
application with both the clock and the data lines being
sent through optocouplers. The figure shows data and
clock signals at the inputs and outputs of the optocou-
plers. To obtain the maximum data transmission rate, both
edges of the clock signal are being used to clock the data;
if only one edge were used, the clock signal would need
to be twice as fast.
Propagation delay skew represents the uncertainty of
where an edge might be after being sent through an
optocoupler.
Figure 10 shows that there will be uncertainty in both
the data and the clock lines. It is important that these
two areas of uncertainty not overlap, otherwise the clock
signal might arrive before all of the data outputs have
settled, or some of the data outputs may start to change
before the clock signal has arrived.
From these considerations, the absolute minimum pulse
width that can be sent through optocouplers in a parallel
application is twice t
slightly longer pulse width to ensure that any additional
uncertainty in the rest of the circuit does not cause a
problem.
The t
guaranteed specifications for propagation delays, pulse-
width distortion and propagation delay skew over the
recommended temperature, and power supply ranges.
Figure 10. Parallel data transmission example
CLOCK
CLOCK
DATA
DATA
PSK
PSK
specified optocouplers offer the advantages of
can determine the maximum parallel data
PSK
t
PSK
is the difference between the shortest
PSK
. A cautious design should use a
t
PSK
PLH
PLH
or t
or t
PHL
PHL
, and the longest
. As mentioned