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LP2980-ADJ: Spice Model

Go Bravos
Expert 6090 points
Part Number: LP2980-ADJ
Other Parts Discussed in Thread: TPS7A24,

Hi team,

Can you provide a spice model for the LP2980IM5-ADJ?

Thank you.

  • 0
    TI__Mastermind 44605 points

    Hello,

    We do not have a model for this device. At this time there is no plan to release one.

    Regards,

    Nick

  • 0 in reply to Nick Butts
    TI__Expert 6090 points

    Hi Nick,

    Is there a similar device that has a spice model that we can point customers to?

  • 0 in reply to Go Bravos
    TI__Mastermind 44605 points

    Hello,

    The product page for LP2980-ADJ recommends TPS7A24 as an alternative device that has the same functionality and it has a PSPICE model available. 

    Regards,

    Nick

  • 0 in reply to Nick Butts
    TI__Expert 6090 points

    Nick,

    Thanks. We are seeing a very rare and intermittent function of the LP2980IM5-ADJ (we believe). The issue only occurs during temperature transitions from cold to hot. It may occur once or a few times and then never again. The issue we are seeing is an incorrect output voltage. The voltage at the ADJ pin is the same for the correct voltage and incorrect output voltage. It seems the only thing that could cause this would be; the feedback resistors’ resistance has change or there was a shift in the internal reference of the regulator.

    Any ideas?

  • 0 in reply to Go Bravos
    TI__Mastermind 44605 points

    Hello,

    If the ADJ voltage has not changed when the output voltage is incorrect then it is not an issue with the internal reference. It must be the feedback resistors changing resistance. 

    How far off is the output voltage? Does it recover after some amount of time? Have they tried measuring the feedback resistors?

    Regards,

    Nick

  • 0 in reply to Nick Butts
    TI__Expert 6090 points

    Hi Nick,

    The output voltage is off by a couple volts.  Based on the performance of the unit under test during this condition, the regulator appears to recover after a certain amount of time.  We have not measured the feedback resistors when this issue occurs.  The big problem is the infrequency and lack of repeatability of this condition.  It only occurs during a temperature transition (cold to hot) and not consistently.

    I think I understand your position on the reference voltage not changing.  Is it possible the pass transistor setting the output voltage could drift?  The same error voltage to the transistor would cause a different output voltage? 

  • 0 in reply to Go Bravos
    TI__Mastermind 44605 points

    Hello,

    It's possible that the RDS(on) could change a bit but that wouldn't manifest as an incorrect output voltage. If the ADJ voltage is correct but the output is wrong then the LDO is doing its job (which is to regulate the ADJ voltage) correctly. If the feedback resistance has changed then the output voltage required to regulate ADJ properly is changed as well.

    Regards,

    Nick

  • 0 in reply to Nick Butts
    TI__Expert 6090 points

    Hi Nick,

    So the feeling is, there’s nothing in the regulator that could create this behavior?  I’ve never seen a condition where a resistor value intermittently changes.  I’m not saying it could not happen, it just seems odd.

  • 0 in reply to Go Bravos
    TI__Mastermind 44605 points

    Hello,

    I can't say definitively that that is true, but based on what you have told me it does not sound like the LDO is behaving abnormally. 

    Do they know at what temperature the output voltage changes and how quickly they are sweeping the temperature? I agree that it seems odd because I haven't looked into changes in resistance with temperature myself but I know that material properties can change with temperature in general. 

    Regards,

    Nick