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Data subject to change. Copyright © 2005-2013 Avago Technologies. All rights reserved. Obsoletes AV01-0565EN

AV02-0876EN - April 5, 2013

Power Supplies and Bypassing

The recommended PROFIBUS application circuit is

shown in Figure 23. Since the HCPL-772X/072X are fully

compatible with CMOS logic level signals, the optocoup-

ler is connected directly to the transceiver. Two bypass

capacitors (with values between 0.01 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. For each capacitor, the total lead length be-

tween both ends of the capacitor and the power supply

pins should not exceed 20 mm. The bypass capacitors

are required because of the high-speed digital nature of

the signals inside the optocoupler.

Being very similar to multi-station RS485 systems, the

HCPL-061N optocoupler provides a transmit disable

function which is necessary to make the bus free after

each master/slave transmission cycle. Specifically, the

HCPL-061N disables the transmitter of the line driver by

putting it into a high state mode. In addition, the HCPL-

061N switches the RX/TX driver IC into the listen mode.

The HCPL-061N offers HCMOS compatibility and the

high CMR performance (1 kV/

sential in industrial communication interfaces.

Figure 23. Recommended PROFIBUS application circuit

1

2

3

8

6

4

7

5

VDD2

VO

GND2

VDD1

VIN

GND1

HCPL-772x

HCPL-072x

8

7

6

1

3

5

2

4

VDD1

VIN

GND1

VDD2

VO

GND2

HCPL-772x

HCPL-072x

5 V

0.01

µF

0.01

µF

0.01

µF

0.01

µF

R

A

SN75176B

VCC

GND

DE

B

0.01

µF

ISO 5 V

1 M

0.01

µF

+

–

GALVANIC

ISOLATION

BOUNDARY

5 V

ISO 5 V

RE

D

1

4

3

2

Rx

ISO 5 V

Tx

8

7

6

1

3

5

2

4

ANODE

VCC

VO

GND

5 V

0.01

µF

ISO 5 V

Tx ENABLE

CATHODE

VE

680

Ω

HCPL-061N

1, 0 k

Ω

5

7

6

8

RT

SHIELD