Datasheet
17
Figure 20. Isolated node providing power to the network.
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 ve (5)
volts locally. The AC line also powers a 24 volt isolated
supply, which powers the network, and another ve-volt
regulator, which, in turn, powers the transceiver and iso-
lated (network) side of the two optocouplers. This meth-
od 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.
NODE/APP SPECIFIC
uP/CAN
HCPL
772x/072x
HCPL
772x/072x
TRANSCEIVER
5 V REG.
V+ (SIGNAL)
V– (SIGNAL)
V+ (POWER)
V– (POWER)
GALVANIC
ISOLATION
BOUNDARY
AC LINE
DRAIN/SHIELD
SIGNAL
POWER
HCPL-0710 fig 20
ISOLATED
SWITCHING
POWER
SUPPLY
5 V REG.
DEVICENET NODE
Figure 19. Isolated node with transceiver powered by the network.
NODE/APP SPECIFIC
uP/CAN
HCPL
772x/072x
HCPL
772x/072x
TRANSCEIVER
NON ISO
5 V
REG.
NETWORK
POWER
SUPPLY
V+ (SIGNAL)
V– (SIGNAL)
V+ (POWER)
V– (POWER)
GALVANIC
ISOLATION
BOUNDARY
AC LINE
DRAIN/SHIELD
SIGNAL
POWER
HCPL-0710 fig 19
*HCPL
772x/072x
* OPTIONAL FOR BUS V + SENSE
More importantly, the unique “dual-inverting” design of
the HCPL-772X/072X ensure the network will not “lock-
up” if either AC line power to the node is lost or the node
powered-o. Specically, when input power (V
DD1
) to the
HCPL-772X/072X located in the transmit path is eliminat-
ed, a RECESSIVE bus state is ensured as the HCPL-772X/
072X output voltage (V
O
) go HIGH.