Datasheet

17
Figure 24. Recommended PROFIBUS application circuit.
Power Supplies and Bypassing
The recommended PROFIBUS application circuit is
shown in Figure 24. Since the HCPL-x710 are fully com-
patible with CMOS logic level signals, the optocoup -
ler is connected directly to the transceiver. Two bypass
capacitors (with values between 0.01 and 0.1 µF) are
required and should be located as close as possible to
the input and output power-supply pins of the HCPL-
x710. For each capacitor, the total lead length between
both ends of the capacitor and the power supply pins
should not exceed 20 mm. The bypass capacitors are
required because of the high-speed digital nature of the
signals inside the optocoupler.
Being very similar to multi-station RS485 systems, the
HCPL-061N optocoupler provides a transmit disable
function which is necessary to make the bus free after
each master/slave transmission cycle. Specically, the
HCPL-061N disables the transmitter of the line driver
by putting it into a high state mode. In addition, the
HCPL-061N switches the RX/TX driver IC into the listen
mode. The HCPL-061N oers HCMOS compatibility and
the high CMR performance (1 kV/µs at V
CM
= 1000 V)
essential in industrial communication interfaces.
HCPL-0710 fig 23
1
2
3
8
6
4
7
5
V
DD2
V
O
GND
2
V
DD1
V
IN
GND
1
HCPL-x710
8
7
6
1
3
5
2
4
V
DD1
V
IN
GND
1
V
DD2
V
O
GND
2
HCPL-x710
5 V
0.01 µF
0.01 µF
0.01
µF
0.01
µF
R
A
SN75176B
V
CC
GND
DE
B
0.01
µF
ISO 5 V
1 M
0.01 µF
+
–
GALVANIC
ISOLATION
BOUNDARY
5 V ISO 5 V
RE
D
1
4
3
2
Rx
ISO 5 V
Tx
8
7
6
1
3
5
2
4
ANODE
V
CC
V
O
GND
5 V
0.01
µF
ISO 5 V
Tx ENABLE
CATHODE
V
E
680 Ω
HCPL-061N
1, 0 kΩ
5
7
6
8
RT
SHIELD