Datasheet

14
Figure 20. Isolated node with transceiver powered by the network.
Isolated Node with Transceiver Powered by the Network
Figure 20 shows a node powered by both the network
and another source. In this case, the transceiver and
isolated (network) side of the two optocouplers are
powered by the network. The rest of the node is
powered by the AC line which is very benecial when
an application requires a signicant amount of power.
This method is also desirable as it does not heavily load
the network.
More importantly, the unique “dual-inverting” design
of the HCPL-x710 ensure the network will not “lock-up”
if either AC line power to the node is lost or the node
powered-o. Specically, when input power (V
DD1
) to
the HCPL-x710 located in the transmit path is eliminat-
ed, a RECESSIVE bus state is ensured as the HCPL-x710
output voltage (V
O
) go HIGH.
*Bus V+ Sensing
It is suggested that the Bus V+ sense block shown in
Figure 20 be implemented. A locally powered node with
an un-powered isolated Physical Layer will accumulate
errors and become bus-o if it attempts to transmit. The
Bus V+ sense signal would be used to change the BOI
attribute of the DeviceNet Object to the “auto-reset”
(01) value. Refer to Volume 1, Section 5.5.3. This would
cause the node to continually reset until bus power was
detected. Once power was detected, the BOI attribute
would be returned to the “hold in bus-o” (00) value.
The BOI attribute should not be left in the “auto-reset”
(01) value since this defeats the jabber protection ca-
pability of the CAN error connement. Any inexpensive
low frequency optical isolator can be used to implement
this feature.
NODE/APP SPECIFIC
uP/CAN
HCPL
0710
HCPL
0710
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
0710
* OPTIONAL FOR BUS V + SENSE