HCPL-063A-000E Datasheet, PDF (16/17 Pages) AVAGO TECHNOLOGIES LIMITED – HCMOS Compatible, High CMR, 10 MBd Optocouplers

V_CC
74HC00
(OR ANY
OPEN-COLLECTOR/
OPEN-DRAIN
LOGIC GATE)
820 Ω
HCPL-261X
1
2
LED
3
4
V_CC
74HC04
(OR ANY
TOTEM-POLE
OUTPUT LOGIC
GATE)
1N4148
750 Ω
HCPL-261A/261N
1
2
LED
3
4
Figure 23. TTL open-collector/open drain gate drive circuit for
HCPL-261A/-261N families.
Figure 24. CMOS gate drive circuit for HCPL-261A/-261N families.
Table 1. Effects of Common Mode Pulse Direction on Transient I_LED


If dV_CM/dt Is:
then I_LP Flows:
and I_LN Flows:
positive (>0)
away from LED
away from LED

anode through C_LA cathode through C_LC
negative (<0) toward LED
toward LED

anode through C_LA cathode through C_LC
If |I_LP| < |I_LN|,
LED I_F Current
Is Momentarily:
increased
decreased
If |I_LP| > |I_LN|,
LED I_F Current
Is Momentarily:
decreased
increased
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 sys-
tem. The propaga­tion delay from low to high (t_PLH) is the
amount of time required for an input signal to propa-
gate 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 9).
Pulse-width distortion (PWD) results when t_PLH and t_PHL
differ in value. PWD is defined as the difference between
t_PLH and t_PHL and often determines the maximum data
rate capability of a transmission system. PWD can be ex-
pressed in percent by dividing the PWD (in ns) by the
minimum pulse width (in ns) being transmitted. Typical-
ly, PWD on the order of 20-30% of the minimum pulse
width is tolerable; the exact figure depends on the par-
ticular applic­ ation (RS232, RS422, T-1, etc.).
Propagation delay skew, t_PSK, is an important parameter
to con­sider in parallel data applications where synchro-
nization 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 delay
is large enough it will determine the maximum rate at
which parallel data can be sent through the optocou-
plers.
Propagation delay skew is defined as the difference be-
tween the minimum and maximum propaga­tion delays,
either t_PLH or t_PHL, for any given group of optocouplers
which are operating under the same conditions (i.e., the
same drive current, supply voltage, output load, and op-
erating temperature). As illustrated in Figure 25, if the in-
puts of a group of optocouplers are switched either ON
or OFF at the same time, t_PSK is the differ­ence between
the shortest propagation delay, either t_PLH or t_PHL, and the
longest propagation delay, either t_PLH or t_PHL.
As mentioned earlier, t_PSK can determine the maximum
parallel data transmission rate. Figure 26 is the timing
diagram of a typical parallel data application with both
the clock and the data lines being sent through opto-
couplers.
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