HCPL-7720 Datasheet, PDF (16/18 Pages) Agilent(Hewlett-Packard) – 40 ns Propagation Delay CMOS Optocoupler

Power Supplies and Bypassing
The recommended DeviceNet
application circuit is shown in
Figure 21. Since the HCPL-772X/
072X are fully compatible with
CMOS logic level signals, the
optocoupler is connected directly
to the CAN 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
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.
ISO 5 V
GALVANIC
ISOLATION
BOUNDARY
TX0
0.01 µF
1 V_DD1
V_DD2 8
2 V_IN
7
HCPL-772x
3
HCPL-072x VO 6
4 GND₁
GND₂ 5
GND
RX0
0.01 µF
5 GND₂
GND₁ 4
6 V_O
3
HCPL-772x
7
HCPL-072x VIN 2
0.01
µF
0.01
µF
5V
LINEAR OR
SWITCHING
REGULATOR
+
V_CC
TxD
CANH
+
C4
0.01 µF
82C250
CANL
Rs
REF
RXD
GND
VREF
D1
30 V
+
5 V+
4 CAN+
3 SHIELD
2 CAN–
1 V–
C1
0.01 µF
R1
500 V
1M
8 V_DD2
ISO 5 V
V_DD1 1
5V
Figure 21. Recommended DeviceNet application circuit.
Implementing PROFIBUS with the
HCPL-772X/072X
An acronym for Process Fieldbus,
PROFIBUS is essentially a twisted-
pair serial link very similar to RS-
485 capable of achieving high-speed
communication up to 12 MBd. As
shown in Figure 22, a PROFIBUS
Controller (PBC) establishes the
connection of a field automation
unit (control or central processing
station) or a field device to the
transmission medium. The PBC
consists of the line transceiver,
optical isolation, frame character
transmitter/receiver (UART), and
the FDL/APP processor with the
interface to the PROFIBUS user.
PROFIBUS USER:
CONTROL STATION
(CENTRAL PROCESSING)
OR FIELD DEVICE
PBC
USER INTERFACE
FDL/APP
PROCESSOR
UART
OPTICAL ISOLATION
MEDIUM
TRANSCEIVER
Figure 22. PROFIBUS Controller (PBC).
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