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SN65HVD485E: SN65HVD485EDRG4 to replace LTC1487

Sam Ting
Expert 3560 points
Part Number: SN65HVD485E

Hi team,

We want to apply SN65HVD485EDRG4 to replace LTC1487, but we can't receive data when testing. Could you review the schematic and provide the suggestions? Thanks! 

Best regards,

Sam Ting

  • 0
    TI__Guru 62920 points

    Hi Sam,

    Can you tell if the issue relates to the signal path from TX3 to to TX3+/- or from RX3+/- to RX3?  If you can capture the signal waveforms at the inputs and outputs when this issue occurs I think it will help to debug.

    One issue I see with the schematic is that RI of both transceivers is tied together.  Since there will be some times when both receivers are enabled, having them share a connection could result in them driving opposite states simultaneously.  These would corrupt the data and could result in errors.  I recommend disconnecting RI from U2.

    Another more minor improvement that could be made would be to place a diode in series with the inverter output so that a high level output transfers through an charges C31 quickly but a low level output is blocked (so that C31 discharges slowly through R35).  This should help improve signal integrity of the transmitter output.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    TI__Expert 3560 points

    Hi Max,

    The issue was solved by disconnecting the RI. Thanks for your support!

    Best regards,

    Sam Ting