SN74AVC4T774: Overvoltage fault behavior

Hi Ed,

By the 1.8V regulator failing, I am inferring that the VCCB side is brought down to 0V. In which case, the device will go into partial power down mode, where the outputs are then disabled so there will not be a concern to expose them to the over voltage levels.

Regards,

Jack 

Just the opposite concern. The worst case is the regulator output going to the input voltage (12V). This can happen with a failure of the high side FET inside the regulator or an open feedback resistor.

Hi Ed,

The AVC4T774 will be damaged if exposed to 12V. This is above the absolute maximum ratings that this device can tolerate. (max is 4.6V)

Regards,

Jack

Yes, the part will be damaged (probably severely). But the original question remains: 

"what is likely to happen to the voltages on the VCCA side of the part? Could they be protected, or would they also rise to overvoltage levels?"

If there is no way of knowing, that is an acceptable answer. If VCCA side is protected it saves me a board spin.

Perhaps using an isolator like the ISO6520 could protect the input side of the part from an overvoltage on the output side of the part. Any other suggestions are welcome.

Thanks,

Ed