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Isolated PROFIBUS

NVE offers a unique PROFIBUS-compliant isolated RS-485 transceiver, the IL3685.

Extraordinary specifications include a 40 Mbps maximum data rate, up to 50 node fanout, and a 15 kV ESD rating for the bus nodes. The part provides transceiver and isolation functions in a single 0.3"-wide 16-pin SOIC package.

An illustrative PROFIBUS circuit is:
 
PROFIBUS Circuit


The 220 ohm termination resistor, along with another 220 ohm resistor and the other end of the bus, matches the bus impedance to minimize reflections. The 390 ohm "fail-safe" resistors guarantee a known state with no active transceivers. Bypass capacitors should be placed as close as possible to the appropriate IC.

 Isolated PROFIBUS Demonstration

PROFIBUS Evaluation Boards

 IL3685 product details

 IL3685 data sheet


Recommended application bulletins:

  AB-5: Isolated RS-485 and RS-422 (.pdf)
Dramatically reduce chip count and board area with IL400- and IL3000-Series single-chip isolated transceivers.
 
AB-6: RS-485 Systems (.pdf)
Practical tips and rules of thumb for making RS-485 systems work.
 
AB-19: PROFIBUS Compliance: A Hardware Design Guide (.pdf)
Hardware design best practices for Profibus DP nodes. Covers three important but sometimes tricky design considerations: isolation, Profibus compatibility, and bus node polarity.
 
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