HCPL-0721 datasheet(16/18 Pages) AVAGO

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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 5 V local-

ly. The AC line also powers a 24 V isolated supply, which

powers the network, and another 5 V regulator, which, in

turn, powers the transceiver and isolated (network) side

of the two optocouplers. This method is recommended

when there is a limited number of devices on the net-

work, which do not require much power, thus eliminat-

ing the need for separate power supplies.

Figure 19. Isolated node with transceiver powered by the network.

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-off. Specifically, when input power (VDD1) 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 (VO) go HIGH.

NODE/APP SPECIFIC

µP/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

ISOLATED

SWITCHING

POWER

SUPPLY

5 V REG.

DeviceNet Node

NODE/APP SPECIFIC

µP/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

772x/072x

* OPTIONAL FOR BUS V + SENSE

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