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LP3982: LP3982 Fault pin floating

Mia Ma
Intellectual 2515 points
Part Number: LP3982

Hi team,

Here is a confusing item of LP3982ILD-ADJ want to confirm with you.

From our pin function table, it is recommended that fault pin should be pulled up as it's open-drain architecture.

But what if I don't need the fault signal, could I just left this pin floating? If the floating fault will influence my LP3982 normal work?

Thanks 

Best regards

Mia Ma

  • 0
    TI__Genius 14245 points

    Hi Mia, 

    Since it is open-drain you can leave it floating but we generally recommend grounding it to improve thermal dissipation but it is just a recommendation. 

  • 0 in reply to Kyle Van Renterghem
    TI__Intellectual 2515 points

    Hi Kyle,

    thanks for your feedback.

    customer is using our part, but no output with a 3.3Vin, and the SHDN is connecting to Vin directly.And the CC pin is only 1.13V which is not the supposed 1.25V.

    Based on above condition, any root cause may come into your mind? Or it’s may only lead to a damaged part root cause?

    thanks

    best regards 

    mia

  • 0 in reply to Mia Ma
    TI__Genius 14245 points

    Hi Mia, 

    from your description of the conditions nothing obvious is wrong, note that the CC pin is a high impedance node so a DMM or scope on that pin could result in a lower reading. The only thing I can think is maybe something is wrong with SET

    • Is the SET pin correctly set using the external resistor dividers? 
      • Is there a short or leakage path from SET to a voltage higher than the voltage on CC (this would cause the LDO to think that Vout is already at or above the correct voltage and it would make the output high impedance resulting in a low output voltage). 
  • 0 in reply to Kyle Van Renterghem
    TI__Intellectual 2515 points

    Hi Kyle,

    they are using our LP3982ILD-ADJ version, use the upper divided resistor 4.53k, lower diviced resistor 10k, and confirm that there is no short condition at the output side.

    Could we get the part is broken already conclusion?

    Thanks

    Best regards

    Mia Ma

  • 0 in reply to Mia Ma
    TI__Genius 14245 points

    Hi Mia, 

    It does seem like the part may be broken, note that every device is tested before being shipped so it is unlikely to have shipped from TI in a broken state. The customer should evaluate possible ways it was damaged after receiving the device, possible causes could be ESD damage, over voltage in the applications or during their testing. 

  • 0 in reply to Kyle Van Renterghem
    TI__Intellectual 2515 points

    Hi Kyle,

    Got it and many thanks.

    Best regards

    Mia Ma