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LM74500-Q1: LM74500-Q1 Reverse Polarity. Need to tolerate 110V positive

Jeremy Richardson
Prodigy 150 points
Part Number: LM74500-Q1
Other Parts Discussed in Thread: LM74502-Q1

Tool/software:

Hello,

I'm looking at using the LM74500-Q1 for reverse polarity protection of -40V.  I need to tolerate +110V surge which is very low impedance.  The LM74500 is only rated for 65V.  Any reason I can't float this with a resistor from the gnd lead to the power gnd and have zeners across the source to ground  terminals of the IC to limit to < 65V?  It would be always on and I would tie enable to source.  It seems like this should be able to be done, but I don't see any application notes recommending this for using at higher bus voltages so I thought maybe I was missing something and wanted to double check.  I was hoping you actually had an app note showing this.

Regards

Jeremy

  • 0
    TI__Mastermind 47230 points

    Hi Jeremy,

    Yes, you can add circuits to protect the controller (LM74500) but your downstream load will not be protected. To protect the load, you will need a blocking FET.

    You can consider LM74502-Q1 which has what you are looking for.

    Regards,

    Shiven Dhir