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SN65HVD12: Application Suggestions

andy lee1
Prodigy 180 points
Part Number: SN65HVD12

Hello,

I would like to ask some questions below,

1. What's the value recommended to the three resistors between the PIN6 & PIN7 ?

2. What's the maximum current of the PIN6 & PIN7 (the driver output or receiver input)?

Thanks for your replying!

  • 0
    TI__Guru 62920 points
    Hi Andy,

    The resistor that connects between the A and B lines (on the far right of the figure) is used for termination. This resistance is generally present at the two furthest nodes of the network and has a value equivalent to the differential characteristic impedance of the wiring, which is typically 120 Ohms for RS-485.

    The series resistors on each line are used to limit the current flowing into the device in the event of an overvoltage condition. These are optional and if used should typically be no greater than 10 Ohms (since their resistance causes a loss of differential voltage amplitude). The maximum current flowing through the A or B pins of SN65HVD12 is 250 mA, which could occur in the event of a short-circuit fault on the RS-485 bus (see "IOS" specification in Table 7.5 of the datasheet).

    Regards,
    Max