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Data subject to change. Copyright © 2005-2013 Avago Technologies. All rights reserved. Obsoletes AV01-0565EN
AV02-0876EN - April 5, 2013
Power Supplies and Bypassing
The recommended PROFIBUS application circuit is
shown in Figure 23. Since the HCPL-772X/072X are fully
compatible 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-
772X/072X. For each capacitor, the total lead length be-
tween both ends of the capacitor and the power supply
pins should not exceed 20 mm. The bypass capac itors
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. Specically, 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 oers HCMOS compatibility and the
high CMR performance (1 kV/µs at V
CM
= 1000 V) es-
sential in industrial communication interfaces.
Figure 23. Recommended PROFIBUS application circuit
1
2
3
8
6
4
7
5
V
DD2
V
O
GND
2
V
DD1
V
IN
GND
1
HCPL-772x
HCPL-072x
8
7
6
1
3
5
2
4
V
DD1
V
IN
GND
1
V
DD2
V
O
GND
2
HCPL-772x
HCPL-072x
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
