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TPS7B4253-Q1: TPS7B4253QDDARQ1 Instability

Hubert Henry, Pecze (Hubie-TSR)
Prodigy 90 points
Part Number: TPS7B4253-Q1

Tool/software:

My customer is constricted in 0805 package, we have been having difficulty finding 22uF automotive grade caps after derating that is above 10uF,

Can you  see if we have stability boundary conditions based on output capacitance like the bottom plot here, that would allow us to decrease the capacitance instead of increasing the capacitance?

  • +1
    TI__Expert 6640 points

    Hey Hubie,

    In our datasheets, we usually we give the recommended minimum output capacitor value, as opposed to minimum capacitance. So in this case, typically a 10uF capacitor, allowing for 30% derating of capacitance, is what is sufficient for stability.

    That being said, it's not immediately clear to me in the datasheet that this distinction between capacitor vs capacitance is also being made for TPS7B4253-Q1 specifically, so let me check and see if I can find any documentation about that.

    Has the customer observed any stability issues with the LDO while using a 22uF output cap?

    Regards,

    Kelsey

  • +1 in reply to Kelsey Farr
    TI__Expert 6640 points

    Hi again,

    I confirmed that 10uF is the minimum output capacitor value. That means the minimum derated capacitance, allowing for 30% derating, is 7uF. 

    So as long as the customer is maintaining >7uF effective capacitance at the output, there should be no stability concerns.

    Regards,

    Kelsey

  • 0 in reply to Kelsey Farr
    TI__Prodigy 90 points

    Kelsey, 

    You're the best! I will follow-up with BW on this and see what they say.

    I will mark this as resolved and if needed, I will reach out again.

    Best,

    Hubie