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SN65HVD3088E: Capacitative loading of cable side I/O pins (A and B).

Robert Pearce
Prodigy 155 points
Part Number: SN65HVD3088E

In order to filter the received signals at the SN65HVD3088E, I have shunted the A and B pins with 100pF capacitors to ground.

Is this acceptable, the data sheet doesn't explicitly say.

  • 0
    TI__Guru 62920 points

    Hi Robert,

    Yes, this is acceptable.  RS-485 networks are often subject to much higher capacitive loading due to the parasitic capacitance of the cabling used, which can be quite long.  At a certain point the low-pass effect will limit the bandwidth of the transmission line (and therefore limit the maximum data rate achievable), but I wouldn't expect 100 pF to cause much degradation.  You can check the A/B signal waveforms to make sure they aren't "rolled off" too much and are able to reach their full-scale amplitudes within a reasonable time to verify there are no issues in this application.

    Regards,
    Max