Isolated Node with Transceiver
Powered by the Network
power to the node is lost or the
node powered-off. Specifically,
when input power (VDD1) to the
HCPL-x710 located in the
transmit path is eliminated, a
RECESSIVE bus state is ensured
as the HCPL-x710 output voltage
(VO) go HIGH.
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-off” (00) value. The
BOI attribute should not be left in
the “auto-reset” (01) value since
this defeats the jabber protection
capability of the CAN error
Figure 20 shows a node powered
by both the network and another
source. In this case, the trans-
ceiver 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 beneficial when
an application requires a
*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-off if it
attempts to transmit. The Bus V+
sense signal would be used to
change the BOI attribute of the
significant amount of power. This
method is also desirable as it does
not heavily load the network.
confinement. Any inexpensive
low frequency optical isolator can
be used to implement this feature.
More importantly, the unique
“dual-inverting” design of the
HCPL-x710 ensure the network
will not “lock-up” if either AC line
AC LINE
NON ISO
5 V
NODE/APP SPECIFIC
uP/CAN
GALVANIC
ISOLATION
BOUNDARY
HCPL
x710
HCPL
x710
*HCPL
x710
REG.
TRANSCEIVER
DRAIN/SHIELD
SIGNAL
V+ (SIGNAL)
V– (SIGNAL)
V+ (POWER)
V– (POWER)
POWER
NETWORK
POWER
* OPTIONAL FOR BUS V + SENSE
SUPPLY
Figure 20. Isolated node with transceiver powered by the network.
13
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
