9
Applications
The HCPL-2300 optocoupler has
the unique combination of low
0.5 mA LED operating drive
current at a 5 MBd speed
performance. Low power supply
current requirement of 10 mA
maximum at 5.25 V and the
ability to provide isolation
between logic systems fulfills
numerous applications ranging
from logic level translations, line
receiver and party line receiver
applications, microprocessor I/O
port isolation, etc. The open col-
lector output allows for wired-OR
arrangement. Specific interface
circuits are illustrated in Figures
12-16, and 18 with correspond-
ing component values, perform-
ance data and recommended
layout in Figures 17 and 19.
For -40°C to 85°C operating
temperature range, a mid-range
LED forward current (IF) of
0.625 mA is recommended in
order to prevent overdriving the
integrated circuit detector due to
increased LED efficiency at
temperatures between 0°C and
-40°C. For narrower temperature
range of 0°C to 85°C, a suggested
operating LED current of
0.75 mA is recommended for the
mid-range operating point and for
minimal propagation delay skew.
A peaking capacitance of 20 pF
in parallel with the current
limiting resistor for the LED
shortens tPHL by approximately
33% and tPLH by 13%. Maintain-
ing LED forward voltage (VF)
below 0.8 V will guarantee that
the HCPL-2300 output is off.
The recommended shunt drive
technique for TTL/LSTTL/CMOS
of Figure 12 provides for optimal
speed performance, no leakage
current path through the LED,
and reduced common mode
influences associated with series
switching of a “floating” LED.
Alternate series drive techniques
with either an active CMOS
inverter or an open collector TTL/
LSTTL inverter are illustrated in
Figures 13 and 14 respectively.
Open collector leakage current of
250 µA has been compensated by
the 3.16 KΩ resistor (Figure 14)
at the expense of twice the
operating forward current.
An application of the HCPL-2300
as an unbalanced line receiver for
use in long line twisted wire pair
communication links is shown in
Figure 15. Low LED IF and VF
allow longer line length, higher
speed and multiple stations on
the line in comparison to higher
IF, VF optocouplers. Greater
speed performance along with
nearly infinite common mode
immunity are achieved via the
balanced split phase circuit of
Figure 16. Basic balanced
differential line receiver can be
accomplished with one HCPL-
2300 in Figure 16, but with a
typical 400 V/µs common mode
immunity. Data rate versus
distance for both the above
unbalanced and balanced line
receiver applications are com-
pared in Figure 17. The RS-232-C
interface circuit of Figure 18
Figure 10. Test Circuit for Common Mode Transient Immunity and Typical Waveforms.
Figure 11. Thermal Derating Curve,
Dependence of Safety Limiting Value
with Case Temperature per
VDE 0884.
OUTPUT POWER – PS, INPUT CURRENT – IS
0
0
TS – CASE TEMPERATURE – °C
20050
400
12525 75 100 150
600
800
200
100
300
500
700 PS (mW)
IS (mA)
175