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LM5069: Current flowing into the OUT pin?

Jake Salmi
Expert 7055 points
Part Number: LM5069

Hi folks - 

I'm looking at a circuit using LM5069.  One of the use cases will have with VIN = 0, VOUT = 12V (from another source on the board), can I get current flowing through the zener diode (the one between GATE and OUT) into the various current sources or the charge pump?  How much current will cause damage? 

Should this be covered in the ABSOLUTE MAXIMUMS Table?

Thanks much 

Jake

  • 0
    TI__Guru** 105361 points
    Hi Jake,

    I hope you are considering back-to-back FET configuration in this use case, else, Vout will appear at Vin through the body diode of the Hot-swap FET.
    Regarding current in to the OUT pin: with reference to the "Figure 18. LM5069EVM-627 Schematic" of www.ti.com/.../slvuaa1.pdf , when both Q1 and Q2 are in OFF condition -> OUT pin does not see 12V, so no current flow is expected in to the OUT pin.
    Let me know if this does not clarify your question.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    TI__Expert 7055 points

    Rakesh, thanks for that application note.

    This question is in regards to a board that already exists with only Q1, so although it is good advice, it is moot for now.

    The use case will have with VIN = 0, VOUT = 12V (from another source on the board), can I get current flowing through the zener diode (the one between GATE and OUT) into the various current sources or the charge pump?  How much current will cause damage? 

    Should this be covered in the ABSOLUTE MAXIMUMS Table?

    Thanks, 

    Jake

  • 0 in reply to Jake Salmi
    TI__Guru** 105361 points
    Hi Jake,

    Let me verify on EVM and get back to you in couple of days.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    TI__Guru** 105361 points
    Hi Jake,

    I did not observed any current flow into the OUT pin on the EVM. Please let me know if you have any queries in this regards.

    Best Regards,
    Rakesh