Broadcom

AV02-0876EN

17

HCPL-0720, HCPL-7720, HCPL-0721,

and HCPL-7721 Data Sheet

40-ns Propagation Delay, CMOS Optocoupler

Isolated Node Providing Power to the Network

Figure 16 shows a node providing power to the network. The AC line powers a regulator which provides 5V locally. The AC

line also powers a 24V isolated supply, which powers the network, and another 5V 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 network, which do not require much power, thus eliminating the need for separate power supplies.

More importantly, the unique dual-inverting design of the HCPL-772X/072X ensure the network will not lock- up if either AC

Figure 16: Isolated Node Providing Power to the Network

The recommended DeviceNet application circuit is shown in Figure 17. Since the HCPL-772X/072X are fully compatible with

CMOS logic level signals, the optocoupler is connected directly to the CAN transceiver. Two bypass capacitors (with values

between 0.01 µF and 0.1 µF) are required and should be located as close as possible to the input and output power-supply

pins of the HCPL-772X/072X. The bypass capacitors are required because of the high-speed digital nature of the signals

inside the optocoupler.

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