HCPL-0720-500E Datasheet, PDF (13/18 Pages) AVAGO TECHNOLOGIES LIMITED – 40 ns Propagation Delay, CMOS Optocoupler

Optical Isolation for Field Bus Networks
To recognize the full benefits of these networks, Avago
optocouplers are recom­mended to provide galvanic iso-
lation. As network communication is bi-directional (in-
volving receiving data from and transmitting data onto
the network), two Avago optocouplers are needed. By
providing galvanic isolation, data integrity is retained
via noise reduction and the elimination of false signals.
In addition, the network receives maximum protection
from power system faults and ground loops.
Within an isolated node, such as the DeviceNet Node
shown in Figure 16, some of the node’s components are
referenced to a ground other than V- of the network.
These components could include such things as devices
with serial ports, parallel ports, RS-232 and RS-485 type
ports. As shown in Figure 16, power from the network is
used only for the transceiver and input (network) side of
the optocouplers.
Isolation of nodes connected to any of the three types of
digital field bus networks is best achieved by using the
HCPL-772X/072X optocouplers. For each network, the
HCPL-772X/072X satisify the critical propagation delay
and pulse width distortion requirem­ ents over the tem-
perature range of 0 °C to +85 °C, and power supply volt-
age range of 4.5 V to 5.5 V.
AC LINE
NODE/APP SPECIFIC
µP/CAN
HCPL
772x/072x
HCPL
772x/072x
TRANSCEIVER
DRAIN/SHIELD
SIGNAL
POWER
NETWORK
POWER
SUPPLY
Figure 16. Typical DeviceNet Node
LOCAL
NODE
SUPPLY
5 V REG.
GALVANIC
ISOLATION
BOUNDARY
V+ (SIGNAL)
V– (SIGNAL)
V+ (POWER)
V– (POWER)
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