13
Shown in Figures 15 and 16 is the
driver interface circuit using a NPN
(2N3904) general-purpose
Table A below lists the
Figure 17 shows an RS-232-E
recommended R (series drive
isolated interface using the
HCPL-0560. The LED is shown
driven with a NPN transistor
(2N3904). The input series
F
current limiting resistor) and R
(output pull-up load resistor) for
the HCPL-0560 optoisolator. The
L
transistor. Since, in a V common
CC
configuration (HCPL-0560) LED
anode for one channel is connected
R values chosen will limit the
F
current limiting resistor R
F
to the V pin of the second
input drive current at the minimum
recommended value of 16 mA. The
(200 Ω) sets the LED current at
16 mA minimum required for the
optoisolator. The pull-up resistor
CC
channel, LED input current now
becomes a direct function of the
power supply voltage. Thus, care
must be taken to use an
appropriate current limiting
resistor, the value of which will be
a function of the common supply
voltage.
R value chosen at each supply
L
voltage will guarantee an output
current does not exceed the
maximum current consistent with
the minimum specified CTR of
15%. Similarly, Table B lists the
R (1.9 kΩ) assures that the
L
optoisolator output will saturate
and conduct current consistent
with the minimum CTR of 15%.
The output of the optoisolator is
shown to interface directly with
DS14C232 (transceiver for
recommended R and R for the
F
L
HCPL-0561 configuration.
RS-232-E) driver input. The
output of the transceiver is shown
to drive the input of NPN
Transistor (2N3904). This NPN
transistor is configured to drive
the LED of the optoisolator.
Table A. HCPL-0560 Input/Output Current Limiting Resistors
V
CC1
or V
5
R (Ω)
R (Ω)
CC2
F
L
188
500
1.9
4.0
6.0
8.2
Similarly Figure 18 shows an
RS-232-E isolated interface using
the HCPL-0561. Again, NPN
transistor 2N3904 is used to drive
the LED of the optoisolator. And
the output of the optoisolator is
directly connected to the driver
input of the transceiver
10
15
20
812
1125
(DC14C232).
Table B. HCPL-0561 Input/Output Current Limiting Resistors
V
CC1
or V
5
R (Ω)
R (Ω)
CC2
F
L
218
531
1.9
4.0
6.0
8.2
10
15
20
843
1156
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
