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SN65HVD10: Application Inquiry

Renan Santos Adriano
Mastermind 22380 points
Part Number: SN65HVD10

Hello Team,

My customer has this transceiver SN65HVD10D. We see in various evaluation kits, designs here and there, and forums pull-up resistors on the A pin and pull-downs on the B pin.
Could you please let me know if and why this is needed? I get conflicting information that it is needed and that it can also cause damage to the transceivers.
the image I sent below would be the "master" RS485 driver, there is a slave one connected to the master.
FPGA <-> Master SN65HVD10D <->Bus of 3meters <->SN65HVD10D <->Slave FPGA

Regards,

Renan

  • 0
    Guru 317260 points

    These are failsafe biasing resistors to ensure a known bus state when the bus is idle; see Application Note 847.

    These resistors cannot damage the transceiver.

    You need these resistors only if there is at least one transceiver without a built-in failsafe mechanism, or if you need to handle noise voltages larger than what the built-in protection is designed for. (The SN65HVD10 has built-in protection against open circuit, idle bus, and shorted bus.)