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SN65HVD10 TVS Application

Seishin
Genius 4135 points

Hello,

I have a question about TVS application.

www.ti.com/.../sn65hvd10.pdf

I think that the recommended value of this series resistance is between 10Ω and 20 Ω.

However, my customer uses 100 Ω.

Is there a possibility that cannot communicate normally?

Best regards,
Seishin

  • 0
    TI__Guru 62920 points
    Hi Seishin,

    Yes, 100 Ohms is too large of a series resistance. Since the RS-485 bus should have 120-Ohm termination at both endpoints, the effective bus loading will be 60 Ohms (120 Ohms || 120 Ohms). Having 100 Ohms in series on both lines would cause the transmitted signal to be attenuated by a factor of about 77%. Resistances in the 5 Ohm to 10 Ohm range would be more appropriate.

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Genius 4135 points
    Hello Max,

    Thank you for your prompt reply.

    Understood.

    I'll tell my customer to change the resistance value.

    Thank you very much.
    Seishin