Input voltage at bus terminal of these RS485 transceivers LTC2862H

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

Hello NQuinn, 

Do you have any update according to my latest comment? Thanks. 

Best,
Nancy

Hi Nancy,

Thank you for the detailed description, this is very helpful.  

I have confirmed with our design team that there is no problem with a differential A-B voltage of +16V or -16V while at a common mode voltage of 8V for regular operation. Your use case is within the normal operating bounds of the LTC2862

Any voltages on the A or B pins within the +/-25V common mode range can be reliably placed on the A and B pins for the lifetime of the device.  

Regards,

Neil 

Hi NQuinn, 

Thank you for you response. That's good to hear. 
I forgot to stress this in my second comment but stated in my original question, our application also include one scenario with A line at +24V and B line at GND (or vise versa) for extended periods of time when not transmitting or receiving data. 

Will LTC2862 handle it with only +1V margin regarding the +/-25V common mode range?

Best,
Nancy

Hi Nancy, 

This second condition is also no problem, in reality for reliable long term/lifetime operation, there is a very large margin to the stated +/-25V common mode range 

Regards,

Neil 

Okay great. Thanks for the confirmation. 
Have a good day!