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  • TI Thinks Resolved

TPS7A85A: Start up Response

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Replies: 3

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Part Number: TPS7A85A

Hi

My customer has question.

Looking at Figure 72 of the TPS7A85A data sheet, the output voltage does not rise to 100% when CNR = 10 nf ~.(Approximately about 90%)
It takes a very long time from 90% to 100%.
Please tell me the reason for this behavior.

Best Regard

T Kishi

  • Hi T,

    according to figure 47 of datasheet charging of CNR/SS is a two phase process: First CNR/SS is charged by INR/SS. Later CNR/SS is charged by RNR, which drives a much smaller current into CNR/SS.

    Kai

  • In reply to kai klaas69:

    Hi kai

    Thank you for reply.

    I understand there are two phases.
    However, there is no provision for the timing at which the phase process.
    Is not it to detect that the output voltage has risen to 100%?Or will you switch around 90%?

    The RNR is described as 250 kΩ, and it can be assumed that the current is about 3.2 uA at Vref = 0.8 V. Since INR / SS = 6.2 uA, I think that it is not a very small current even if phase switching, but why is the rise so late?

    Regard

    T Kishi

  • In reply to T Kishi:

    Hi T,

    please have a look at figure 17 again. The final output voltage is 0.9V. The rise time isn't so long if CNR/SS is 10nF...

    Kai

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