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THVD4431: Termination Resistor

Hisao Uchikoshi
Genius 14650 points
Part Number: THVD4431

Hi Experts,

My customer wants to use RS232C and RS485((full-duplex mode). The termination resister can be enabled or disabled using pins. When setting TERM_TX = VIO and TERM_RX = VIO, the termination resister is enabled when RS-485 mode is enabled and disabled when RS232C mode is enabled. In other words, customer does not need to control TERM_TX pin and TERM_RX pin by external device to enable and disable the internal termination resister.

Is this understanding correct?

regards,

Uchikoshi

  • +1
    Guru 314580 points

    RS-232 always uses point-to-point connections and requires a 50 kΩ pull-down at the receiver. This is enabled/disabled automatically.
    RS-485 can use larger buses, where termination must be enabled only at the two ends. Therefore, RS-485 termination can be externally controlled.

    You are correct that the TERM_xX pins do not need to be controlled if you always want to enable termination in RS-485 mode. But if it is possible that the THVD4431 is connected to the middle of a bus, then it would be necessary to be able to disable the resistors.