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LM2597: LM2597HVM-5.0/NOPB Pin 5 operation

Todd Montgomery
Prodigy 200 points
Part Number: LM2597
Other Parts Discussed in Thread: LMR43610, LMR36506

We have been using the LM2594HVM-5.0/NOPB for a design for years.  However, this part is not available.  We also do that the LM2597HVM-5.0/NOPB is similar but the SS pin 5 is a different polarity.

We are wondering if we can use the same part essentially, leave pin 1 2, and 5 unconnected and get the same performance?  The datasheet for the LM2597HVM-5.0/NOPB does not say if that pin can be left disconnected or does it need to be pulled high in a known state for the IC to work as expected.

  • 0
    TI__Mastermind 35190 points

    Hello,

    My gut reaction is that the performance with that pin being N/C, the behavior would indeterministic. If pins are acceptable to be N/C it is often mentioned in datasheet. Sometimes their is a current sink/source on pin to pull a pin a certain direction (usually to an inactive state).

    We can't advise anything that isn't specified in the datasheet, though I will check with the designer whom supports this product. I am sure he will have some uncertainty as well given the age of the device, so my recommendation would be to consider a newer device with potentially higher availability. IE: LMR36506, LMR43610.

  • 0 in reply to Marshall_Beck
    Prodigy 200 points

    This IC is to replace the LM2594HVM-5.0/NOPB in an existing design, which does not seem to be available.  So I was hoping to keep the same footprint.

    Thank you.

  • 0 in reply to Todd Montgomery
    TI__Mastermind 35190 points

    Hello Todd,

    I spoke with the designer and he confirmed that leaving that pin open on the device may not be a desirable implementation as the output voltage may have an overvoltage transient, as this pin will be pulled up quickly without any capacitance on it.

    Even with some capacitance, it is not a vetted nor recommended solution.