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SN74LVC541A input ratings

Kevin Benstead87
Prodigy 50 points
Other Parts Discussed in Thread: SN74LVC541A

Hi

I'm using an SN74LVC541A to drop some normally 5V signals down to 3.3V (VCC for the device).  the datasheet says this is OK.

My problem is that my signal source could under a single fault condition rise up to 24V.

The data sheet has a note in section 7.1 (absolute maximum ratings) which reads "(2) The input negative-voltage and output voltage ratings may be exceeded if the input and output current ratings are observed."  

I had originally mis-read this statement as applying tom both negative and positive voltage ratings.  But it only applies to input voltages less than 0V,  What about voltages greater than the 6.5V maximum rating.

I've got lots of resistance in series with the input such that if the fault occurred the current into the device would be no more than about 40uA.

Would this damage the device.

 Thanks

  • 0
    TI__Guru 62100 points
    Hi Kevin ,

    Unfortunately , you are violating the abs max ratings . 24V is way beyond the process handling capability and with all the current limiting implemented could be damaging to the device as it is not built to handle such high voltage . It is a different issue when talking about violating voltage within the process capability by 0.5 -1V higher but a different issue when it is 20V higher .
    The device being robust , might sustain it for sometime but greatly reduces its stability. The reliability of the part and the system might be greatly compromised with this .
    you might have to choose a device tolerating higher voltage (CD4K abs max has 20V ) but still might need external protection to bypass the event .