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Input voltage at bus terminal of these RS485 transceivers LTC2862H

Hi. 

What is the input voltage at bus terminal of LTC2862H?

We have our own special application on RS485 transceiver like below,


RS485 Master: connect B to GND and connect A to 12-16V.

RS485 Slave: one(can be A or B) to GND minus one diode and one(can be A or B) to 12-16V (possible 24V) minus one diode.

Will the LTC2862H be able to handle LTC2862H with the application above?

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  • Hello, 

    The bus pins of the LTC2862H are rated to -60V to +60V.

    The receiver will function correctly across a common mode range of -25V to +25V. 

    LTC2862 would handle this use case without any issue. 

    Regards,

    Neil 

  • Hi Neil, 

    Thanks for your response. 

    -60 to +60 V is fault protection overvoltage for absolute maximum ratings NOT "recommended operating conditions". In our application, 16V is applied constantly and for a very long time. -60 to 60V applies to short time but not a long time scenario if I understand correctly? The differences between A and B in our application is 12-16V, meaning the common mode voltage will be 8V. This is totally within+-25V. But it’s not the common mode voltage we are worried about.

    My question is:  Can these transceivers handle the A line at +16V and B line at GND (or vise versa) for extended periods of time when not transmitting or receiving data.? These transceivers are not driving or reading the 16V signal, they are just on the same bus. At some point this 16V signal turns off and the bus returns to being an RS485 bus where these drivers can operate as expected in a "regular" RS485 type system.

    I hope explanation above clarify my question better. 

    Best,
    Nancy

Reply
  • Hi Neil, 

    Thanks for your response. 

    -60 to +60 V is fault protection overvoltage for absolute maximum ratings NOT "recommended operating conditions". In our application, 16V is applied constantly and for a very long time. -60 to 60V applies to short time but not a long time scenario if I understand correctly? The differences between A and B in our application is 12-16V, meaning the common mode voltage will be 8V. This is totally within+-25V. But it’s not the common mode voltage we are worried about.

    My question is:  Can these transceivers handle the A line at +16V and B line at GND (or vise versa) for extended periods of time when not transmitting or receiving data.? These transceivers are not driving or reading the 16V signal, they are just on the same bus. At some point this 16V signal turns off and the bus returns to being an RS485 bus where these drivers can operate as expected in a "regular" RS485 type system.

    I hope explanation above clarify my question better. 

    Best,
    Nancy

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