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UCC28180: RISENSE_filter

K.Yaita
Guru 29720 points

Part Number: UCC28180

Hi Team,

The datasheet recommends 220ohm for RISENSE_filter.
Is it no ploblem if we use more than 220ohm?
My customer wants to adjust CISENSE_filter value because of short supply.






Best Regards,
Yaita

  • 0
    TI__Mastermind 34465 points
    Hello Yaita,
    The purpose of RISENSE and CISENSE is to filter out any noise spikes from the low level current signal on the current sense pin input , ISENSE.
    Normally RISENSE is set at 220 Ohms and CISENSE is set at 1000pF. This gives you a time constant of about 0.22uSecs.
    If you keep the RC time constant approximately the same then there will not be a problem.
    For example you can make RISENSE = 330 Ohms and CISENSE = 660pF.
    Do you know what value of resistor your customer is planning to use ?
    Regards
    John
  • 0 in reply to John Griffin1
    Guru 29720 points

    Hi John-san,

    Thank you for your support!
    I would like to ask one more.

    The datasheet shows 1000pF for CISENSE as the following.
    ------------------------------------------------
    (datasheet page 28)
    To protect the device from inrush current, a standard 220-Ω resistor, RISENSE, is placed in series with the ISENSE pin.
    A 1000-pF capacitor is placed close to the device to improve noise immunity on the ISENSE pin.
    ------------------------------------------------

    On the other hand, Design Calculator recommends calculated value (not fixed value).


    Which is recommended value 1000pF or the value calculated by Design Calculator?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 34465 points
    Hi Yaita-san,
    Please use a value close to the recommended value in the calculator tool. In this case use 680pF
    Regards
    John
  • 0 in reply to John Griffin1
    Guru 29720 points

    Hi John-san,

    Thank you for your support. I understand.
    I believe it is better adding calculation formula for CISENSEfilter in datasheet.
    What do you think about it?

    Best Regards,
    Yaita