SN65HVD1473: Termination resistor in RS-485 mode.

Oscar Gomez Fuente

Expert 2061 points

Part Number: SN65HVD1473

Hi everyone,

I'm using the SN65HVD1473 transceiver in RS-485 mode. Does the termination resistor have to be Pulse-Proof?

Best regards.

over 7 years ago

0 Miguel Robertson over 7 years ago

TI__Guru 62910 points

Hi Oscar,

No, this is not required by the transceiver and is generally not needed for system robustness. Any large voltage pulses would result in high pulse currents into the transceiver device (which is designed to handle them up to a certain extent) and through any series components on the RS-485 lines, not the termination resistance. The only exceptions might be if one side of the termination is shorted to ground or power during a fault condition or if large differential voltage pulses are present (this would not be typical).

Max

0 Oscar Gomez Fuente over 7 years ago in reply to Miguel Robertson

Expert 2061 points

Thank you Max,

But the resistors in serie of 10 Ohms have to be Pulse-Proof, don't they?

Best regards.

0 Miguel Robertson over 7 years ago in reply to Oscar Gomez Fuente

TI__Guru 62910 points

Yes, this is generally a good idea since any large transients would need to flow through these series resistances as they make their way through the clamping structures within the transceiver to ground.

Max

0 Oscar Gomez Fuente over 7 years ago in reply to Miguel Robertson

Expert 2061 points

Hi Max,

And the typical pull-up and pull-down resistors of 560-470 Ohms, Do they have to be pulse-proof?

Best regrds.

0 Miguel Robertson over 7 years ago in reply to Oscar Gomez Fuente

TI__Guru 62910 points

Typically not, since the higher resistances will limit the current that flows through them during a transient event. It may be beneficial to make them pulse proof if the system needs to survive particularly severe transients, though.

Max

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SN65HVD1473: Termination resistor in RS-485 mode.