acpl-w70l Avago Technologies, acpl-w70l Datasheet - Page 10

• Manufacturer Part Number: acpl-w70l
• Description: Single-channel And Dual-channel High Speed 15 Mbd Cmos Optocoupler With Glitch-free Power-up Feature
• Manufacturer: Avago Technologies

GND1
Figure 8. Recommended printed circuit board layout
V
V
Figure 9. Propagation delay skew waveform
time, t
tion delay, either t
delay, either t
termine the maximum parallel data 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 op-
tocoupler.
10
V
V
O
O
I
I
I
F
PSK
1
2
3
is the difference between the shortest propaga-
ACPL-W70L
PHL
50%
50%
or t
PHL
CMOS
2.5 V,
PHL
or t
. As mentioned earlier, t
PHL
6
5
4
, and the longest propagation
t
PSK
GND2
C
V
C=0.01µF to 0.1µF
Vo
DD
2.5 V,
CMOS
PSK
GND 1
GND 1
can de-
I
I
F1
F2
1
2
3
4
INPUTS
OUTPUTS
Figure 10. Parallel data transmission example.
Figure 10 shows that there will be uncertainty in both the
data and the clock lines. It is important that these two ar-
eas 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 rec-
ommended temperature, and power supply ranges.
ACPL-K73L
CLOCK
CLOCK
DATA
DATA
PSK
specified optocouplers offer the advantages of
8
7
6
5
t
PSK
GND 2
PSK
C
. A cautious design should use a
t
PSK
V
V
V
DD
O1
O2