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LM27761: LM27761

Dmitri Golovanov
Prodigy 10 points
Part Number: LM27761

Tool/software:

I would like to use  LM27761 to generate -1.3V from +5V.

The part's spec shows the minimum Vout as -1.5V. In the same time, the Vref is 1.22V. Logically, it should be capable to produce -1.3V.

I did the test and indeed it can produce the Vout down to -1.22V.

I would like to get a confirmation that the  Vout = -1.3V does not create any problem with the part.

And I am curious , why the datasheet limits it to -1.5V?

Thank you.

  • 0
    TI__Mastermind 19290 points

    Hello Dmitri,

    thanks for reaching out in E2E.

    The maximum output voltage limit of -1.5V is related to the IC design. Operation outside the spec limits is not recommended.

    Best regards,

    Andreas.

  • 0 in reply to Andreas Mueller
    Prodigy 10 points

    Hi Andreas,
    Thank you for your response.

    Is it possible to provide more details, why it is not recommended? Maybe our use case could be acceptable?

    The Iout in my project is 10mA.

    Can you suggest an alternative from TI?

  • +1
    TI__Mastermind 19290 points

    Hello Dmitri,

    I don't have more details.

    There is also no better alternative part.

    You could add an extra LDO at the output of the LM27761 to regulate to -1.3V. Let me know if this would be an option, then I can contact the LDO team for selecting a suitable part.

    If you don't need the low noise and PSRR of an LDO, then you could also evaluate the option of operating a regular buck converter in inverted buck boost configuration. See this app note for an example: "Using the TPS6215x in an Inverting Buck-Boost Topology".

    You could also combine the inverting buck boost with an extra LDO.

    Please let me know your thoughts.

    Best regards,

    Andreas.