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THVD1451: RS485 short condition detect when using THVD1451

user6060721
Expert 1015 points
Part Number: THVD1451
Other Parts Discussed in Thread: TCAN1043

When I test RS485 communication by using THVD1451,THVD1451 can not detect A short to GND、B short to GND、A short to 3.3V、B short to 3.3V.

1.A short to GND :there is no signal on line A,but differential is normal

2.B short to GND: there is no signal on line B,and differential have some error data

3.A short to 3.3V: line A is high 3.3V,and differential have some error data

4.B short to 3.3V:line B is high 3.3V,idle bus is low,differential have no start signal.

If I want to detect these short condition,can be realized by using THVD1451.

Or I have to change to another transceiver?

If I have to change to another transceiver,which model you recommend?

Thanks.

  • 0
    TI__Mastermind 48195 points

    Hello,

    We don't currently offer any single channel RS-485 devices with integrated fault detection features. You may choose to do this with discrete external components and still include THVD1451 or similar transceiver for typical communication. 

    To detect these faults with an external solution, you may implement some method of measuring the current on the bus. This can be done using small series resistances on the A and B lines and another device to detect some threshold voltage across it. THVD1451 should have no issue driving valid signals through such small series resistances when used in a typical RS-485 network and therefore shouldn't mind the extra circuitry on the bus. 

    I'll also mention that TCAN1043 is a CAN transceiver with integrated fault detection and can detect when one of the differential lines is shorted to GND or Vcc. The current version of the device only reports a general fault (does not specify which fault is present), though future devices will be able to report which fault is detected. You may be able to adapt this device to serve as a dedicated fault detector in your RS-485 system or could serve as an integrated solution if you choose to use the CAN protocol.

    Please let me know if you have any more questions.

    Regards,
    Eric