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LTC2852 with no Vcc and active TxD+ signal

Question asked by apomerants on May 30, 2018
Latest reply on May 31, 2018 by yuanyh

Hi

What will be the behavior of the LTC2852 in case I connect to it a RS422 driver (such as MOXA) that drives a voltage (~4v) over its TxD+ output (as it sends a constant "1" as long as the PC doesn't communicate with it).

I would like to know what will happen in case at this time the card with the LTC2852 was not activated yet, meaning the LTC2852 has a voltage at its positive input pin (pin "A") but has no Vcc?

Does it has a clamping diode that will cause the MOXA voltage to appear on the LTC2852 Vcc pin  ??

Will this "Vcc" parasitic voltage (4V - 0.7V = 3.3V !!) be able to operate the LTC2582?

Will I see any wave coming out of its output pin (pin RO i.e pin #1)?

Does any of the above questions is related with temperature? I am asking as my system FPGA connected to the LTC2582 RO output doesn't wake up properly while powering the system in the oven at -20c temperature..!!??

and I have noticed that if I disconnect the TxD+ signal from entering my system is enough to "ruin" it...

 

Thanks

 

Amnon

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