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TPS7A7001: LDO has short at input after 3 days of operation

Part Number: TPS7A7001

Dear Sir or Madam,

we use several TPS7A7001 in parallel. Each with Cin=10uF, Cout=10uF+4.7uF, giving a total of Cin=150uF.
VIN=5V5, VOUT=between 3V and 5V0.
After three days of operation (VIN from HMP4040) and RLOAD=open, the DC input resistance is around 20 Ohm or less. 
A PDF file with more details is available here: 
This happened to three PCBs of the same type and we have similar problems with LDK130M-R from ST.
Do you have any idea? Stability, cap size ?
The PCB is for power supply of a satellite radar system.
 
Best regards,
mh_
 
  • In reply to mh_:

    ... this would also explain why TPS7A4501KTTR, which we also use, did not crash.
    The datasheet says it includes a reverse current protection.
  • In reply to mh_:

    This would also explain why TPS7A4501KTTR, which we also use, did not crash.
    The datasheet says, it includes a reverse current protection.
  • In reply to mh_:

    Reverse current could definitely be an explanation. Whenever Vout exceeds Vin there is the potential for reverse current. Traditionally LDOs do not contain reverse current protection (some LDOs like TPS709 have this feature added). If reverse current is anticipated in an application, it is a good idea to add external circuitry for the reverse current. The suggestion of adding a Schottky diode is a common and robust method to protect the LDO from reverse current.

    Very Respectfully,
    Ryan
  • In reply to Ryan Eslinger:

    Hello Ryan,

    ok. We will produce new PCBs and use these two types of Schottky diodes from OUTPUT to INPUT.

    de.farnell.com/.../1773475

    de.farnell.com/search

    Anything to say against this choice ?

    Thank you so far ...

  • In reply to mh_:

    Both diodes have low Vf ratings; therefore, as long as the reverse current remains within the rating of the diodes you will be adequately protecting the LDO from reverse current. From the information you have provided, these diodes may be adequate for your design.

    Very Respectfully,
    Ryan
  • In reply to Ryan Eslinger:

    Ok. Thank you Ryan. 

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