ADP7182 - Behaviour after mistaken voltage polarity

Hi,

I have been tasked to troubleshoot a PCB that is powered by an ADP7142-2.5 (providing +2.5V) and an ADP7182-2.5 (providing -2.5V). The ADP7182 was exposed for about to 3-5 seconds to +3.7V (instead of -3.7V), due to the battery being plugged in the wrong way round. It smoked, the user removed the battery, and gave it to me to fix. During testing the regulated output is stable at -2.35V (instead of the expected -2.5V). I have two questions that I hope you could help me with:

1)What is the failure mode of the ADP7182 to such faults? In other words, is it safe to assume that the components downstream were not exposed to the reversely inputted voltage? (My testing seems to suggest so, but I would still really appreciate some input).

2)Is there any indication as to why the output is stable at -2.35V? And moreover, could I assume that it will stay there or is it liable to changing? The exact voltage output is not critical, but I do not want to risk further damage.

Thanks in advance, I truly appreciate any input.

Best,

George

Parents
  • 0
    •  Analog Employees 
    on Apr 12, 2021 1:02 AM

    Hi George,

    To address both your questions, I'll refer you to the Abs Max section of ADP7182. 

    Firstly, the failure mode of ADP7182 not operating as expected is the reverse polarity application. ADP7182 is rated to up to +0.3V only and applying +3.7V which exceeds the rating may have caused permanent damage to the LDO.

    Secondly, behavior beyond the abs max will not be guaranteed to operate as expected. Replace the LDO immediately before retrying your circuit. 

    Best regards,

    Bryan

Reply
  • 0
    •  Analog Employees 
    on Apr 12, 2021 1:02 AM

    Hi George,

    To address both your questions, I'll refer you to the Abs Max section of ADP7182. 

    Firstly, the failure mode of ADP7182 not operating as expected is the reverse polarity application. ADP7182 is rated to up to +0.3V only and applying +3.7V which exceeds the rating may have caused permanent damage to the LDO.

    Secondly, behavior beyond the abs max will not be guaranteed to operate as expected. Replace the LDO immediately before retrying your circuit. 

    Best regards,

    Bryan

Children
  • Hi Bryan,

    Thanks for your reply. I really appreciate your help.

    Just one follow-up question:

    In general, when such reverse polarity is applied to the ldo, how does the output voltage respond? Are the downstream components also exposed to the reverse polarity (and hence at risk of being damaged and need replacing) or does the ldo provide come protection to those components by shorting the reverse current to ground?

    Hope that makes sense.

    Best,

    George

  • 0
    •  Analog Employees 
    on Apr 13, 2021 1:31 PM in reply to G Gryparis

    Hi George,

    The LDO has protection diodes that are the first to respond during a failure event such as reverse polarity input which essentially protects the load side. 

    As mentioned, you should replace the part since its behavior is not guaranteed by the datasheet due to the violation of abs max levels.

    Regards,

    Bryan