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TPS7H1111-SP: LDO basics, capacitance derating

Vijay
Prodigy 170 points
Part Number: TPS7H1111-SP

Hello Team,
I have been reading the document LDO Basics (slyy151a) from TI.
The document refers to the capacitor DC voltage derating.


In the image, the locked dipole seems to align with the applied electric field. While the active dipole doesn't.
What exactly is a locked dipole and an active dipole?
I believe the dipoles in a capacitor need to be aligned with the applied electric field (just like a locked dipole).
Please correct me if I am wrong.

Looking for your reply.

  • 0
    TI__Mastermind 24965 points

    Hey Vijayaraj,

    Dipoles are by definition simply a pair of opposite charges.
    The paper you linked explains that not all of the dipoles align with the applied electric field.
    This picture is trying to demonstrate that.
    This is influenced by the electric field strength.

    The explanation under figure two also goes into what influences this lock mechanism.

    Thanks,
    Daniel

  • 0 in reply to Daniel Hartung
    Prodigy 170 points

    Hello Daniel,
    Thank you for your reply.

    I believe the dipoles in a capacitor need to be aligned with the applied electric field.
    Active dipoles are the contributors to the capacitance of a capacitor.
    Locked dipoles are the reason for capacitance derating.
    Please correct me if I am wrong.

    From figure two the locked dipoles (in red color) seem to be perfectly aligned with the applied electric field.
    Why is that?
    If the locked dipoles are the reason for the capacitive derating, then those dipoles should be misaligned with the applied electric filed.
    Please correct me if I am wrong.

    Looking for your reply.

  • +1 in reply to Vijay
    TI__Mastermind 24965 points

    Hey Vijayaraj,

    Figure 2 does clearly state that locked dipoles influence capacitive derating as less dipoles are locked the better.

    My question to you to help is what happens when two different charges are added together?

    Most of your questions are theoretical in nature would best be answered by a textbook on the subject.

    Thanks,
    Daniel