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LMR12015: Feedforward Capacitor

Shuji Ishiwata
Mastermind 6125 points
Part Number: LMR12015

Hi All,

I have a question about Feedforward Capacitor.

The formula below does not match the capacity of the CFF in Figure 37.
Are there any other conditions or recommended capacitor capacities?

Also, depending on the temperature conditions, the capacity value may not be met. Is there any problem if the capacity cannot be met?

Best Regards,
Ishiwata

  • 0
    TI__Mastermind 46850 points

    Hi Ishiwata,

    Cff as 0.18uF in Figure 37 of datasheet is incorrect and should be typo. 0.18uF is too big and doesn't make sense. The Cff should be lower than 36nF based on equation. Please refer to Figure 41. Fig 41 should be reasonable. Will update the datasheet in next revision. 

    Hope this helps,

    Thanks,

    Nancy

  • 0 in reply to Nancy Zhang
    Mastermind 6125 points

    Hi Nancy

    Thank you for your reply.
    I understand that it is a typo.

    There were no comments on the last question below.
    Can you give us any comments?

    " Also, depending on the temperature conditions, the capacity value may not be met. Is there any problem if the capacity cannot be met? "


    Thank you very much for your support.

    Best Regards,
    Ishiwata

  • +1 in reply to Shuji Ishiwata
    TI__Mastermind 46850 points

    Hi Ishiwata,

    The feedforward capacitance tolerance or variation should not affect the performance. Our equation is equal or less than. You can place Cff as placeholder on the board. You may not need to populate it if the transient performance can meet your requirement.

    Hope this helps,

    Thanks,

    Nancy