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TL7705B: Abuot the value of Ct capacitor

masahiko shimizu
Guru 11235 points
Part Number: TL7705B

Hi,

My customer is using TL7705B.
He has a issue about delay time.

He used 100uF at Ct capacitor.
But at this time, TL7705B does not released reset signal.

and he also confirmed at using 10uF of Ct capacitor.
At this time, TL7705B released the reset normally having 260ms delay.

Does TL7705B have the limitation of Ct capacitor value?

Best regards,
Shimizu

  • 0
    TI__Genius 12630 points

    Shimizu,

    The delay starts when the SENSE is no longer in undervoltage condition. The delay follows: Delay in seconds = 2.6 x 10^4 x Ct where Ct is in units of Farads.

    So with 100uF, this gives a delay of 2.6 seconds.

    With 10uF, this gives a delay of 260ms (as you mentioned).

    The datasheet recommends 0.1uF for 2.6ms delay.

    The minimum limit (with no Ct capacitor) will follow the timing specs found in Table 6.6 on page 5 of the datasheet and will depend on which output at which situation you are looking at.

    I hope this helps you! Let me know if you have more questions. Thank you.

    -Michael