Isolated Node Providing
Power to the Network
Figure 20 shows a node providing
power to the network. The AC line
powers a regulator which
provides five (5) volts locally. The
AC line also powers a 24 volt
isolated supply, which powers the
network, and another five-volt
regulator, which, in turn, powers
the transceiver and isolated
(network) side of the two
optocouplers. This method is
recommended when there are a
limited number of devices on the
network that don’t require much
power, thus eliminating the need
for separate power supplies.
More importantly, the unique
“dual-inverting” design of the
HCPL-0710 ensures the network
will not “lock-up” if either AC line
power to the node is lost or the
node powered-off. Specifically,
when input power (VDD1) to the
HCPL-0710 located in the
transmit path is eliminated, a
RECESSIVE bus state is ensured
as the HCPL-0710 output voltage
(VO) goes HIGH.
AC LINE
DEVICENET NODE
NODE/APP SPECIFIC
5 V REG.
uP/CAN
ISOLATED
SWITCHING
POWER
GALVANIC
ISOLATION
BOUNDARY
HCPL
0710
HCPL
0710
SUPPLY
5 V REG.
TRANSCEIVER
DRAIN/SHIELD
SIGNAL
V+ (SIGNAL)
V– (SIGNAL)
V+ (POWER)
V– (POWER)
POWER
Figure 20. Isolated Node Providing Power to the Network.
HP [ HEWLETT-PACKARD ]
