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TPS7A4001 VOUT in short, open between pins

na na78
Guru 16770 points
Other Parts Discussed in Thread: TPS7A4001

Hi

We have some questions about TPS7A4001DGNR.
If you have answers, could you show us?

1. Can you tell the voltage of OUT pin when the FB pin is shorted to GND or left OPEN? Does some protections work and disable the output?

2. Can you tell the voltage of OUT when the FB and OUT are shorted?

3. Can you tell the voltage fo OUT when the FB and NC pin  (PIN3) are shorted?  The NC pin is not internally connected completely, isn't it?

Best regards

  • 0
    TI__Guru 55940 points
    Hi Na,

    Questions 1 and 3 are the same answer as the datasheet states that the NC pins must be either left open or tied to GND. In both cases, TPS7A4001 will be in dropout. The error amp will be fully cocked and the output will follow the input (minus dropout). Current limit and thermal shutdown will be functional, but there is no additional internal protections.

    If OUT and FB are shorted, the output will be equal to the Vref which is ~1.175 for this device.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Guru 16770 points
    Hi Ryan

    Thank you for your reply.
    We understood that the device operates in dropout mode in case of Question1 and 3.

    Do you have answers to the following question?
    >The NC pin is not internally connected completely, isn't it?

    We should do the short-circuit test for safety. So we want to confirm if "NC" means "Internally open".

    Best regards
  • 0 in reply to na na78
    TI__Guru 55940 points
    Hi Na,

    Correct. The NC pins are not internally connected.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Guru 16770 points
    Hi Ryan

    Thank you for your reply.
    We got it.

    Best regards
  • 0 in reply to na na78
    TI__Expert 6100 points

    Ryan,

     

    I'm TIJ FAE.

    We have additional question for TPS7A4001.

    If GND pin is opened, what happen on Vout ?

    Best regards,

    Harumi Iitsuka

  • 0 in reply to Harumi Iitsuka
    TI__Guru 55940 points

    Hi Harumi,

    The voltage on the GND pin is the reference point for all other voltages with the LDO.  If GND is left floating, by definition we do not know what voltage is on this pin at a given time.  Due to the fact that the reference for Vout (the GND pin) is floating, the Vout will appear to be floating.  However, because an LDO will not generate a higher voltage on the output, Vout will still be limited by the input power supply.  Vout could be any voltage between the input supply ground and Vin.

    Very Respectfully,

    Ryan