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Issue with ISO3088

Miteshkumar Dalabhai Patel
Intellectual 2450 points
Other Parts Discussed in Thread: ISO3082, ISO3088

Hello All

 

We have made the circuit for RS485 to RS485 isolation using ISO3082. This circuit is working perfactly ok at baud rate of 38.4K. I have also checked at 187K & some times interface is failing. So we have replaced the ISO3082 with ISO3088 as it has higher speed. But this circuit is not working even at 9600 baudrate..

 

Pls. guide us for the same.

 

Thanks

mitesh

ECPE238001.pdf
  • 0
    TI__Mastermind 28265 points

    Mitesh,

    I assume your data link between the ISO3082 and the HMI interface is too long to work without termination resistors.

    the ISO3082 has slower rise times and will work without termination for a certain length. however, when increasing the data rate it can loose some data due to reflections.

    The rise times of the ISO3088 are much faster and therefore will fail without termination at much shorter cable length.

    Please insert two 120 ohms termination resistors between the differential data lines, one next to the ISO3082, the other one next to the HMI.

    Best regards,

    Thomas