• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 62 subscribers
  • Views 1022 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC2891: Selecting value for Y safety cap

Serdar Köse
Genius 3360 points
Part Number: UCC2891

Hi,

I am following PMP4447 reference design.  That design  have a 470 pF, Y cap. Another design (PMP30044) uses 3300 pF.  The other reference designs have different values. I wonder one determines that value, is it based on a calculation or based on a measurement? Can I replace 470 pF with 680pF cap that has the same properties? Is it a correct statement to say higher the capacitance the better?

  • 0
    TI__Expert 5900 points
    Hi Serda，
    For safety concern, smaller Y cap is better as bigger value Y cap will cause higher leakage current from primary side to secondary. Many rules based on different equipments/applications has the limitation for leakage current.
    For EMI, a bigger value usually bring better EMI performance.
    So, the general directions are to use as samll Y cap as possible if you could solve EMI problem

    Br
    Kening