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LM20146: Sw frequency

kura
Genius 4840 points
Part Number: LM20146

Our customer has a question about SW frequency of LM20146.

They use 260kohms as RT.

Fsw 247.62kHz  is given from EQ(8) in datasheet P16.

If this frequency set about 200kHz, what kind of problem happen ?

  • 0
    TI__Guru**** 191445 points
    Kura,

    So you are setting Fsw to 247.6 kHz but measuring 200 kHz at the switching node? The frequency could vary from the set point by +/- 13 %. It may also be lower at light loads. Can you post a waveform?
  • 0 in reply to JohnTucker
    Genius 4840 points

    John-san

     

    Thank you for your reply.

     

     No.If they set RT 310kohms(Fsw:200kHz from EQ(8)),is this part operated normaly?

    Does this cause any problem ?

    We can't find min sw frequency of this part.

  • 0 in reply to kura
    TI__Guru**** 191445 points
    Kura-san,

    That frequency is outside of the specified range which is 250 to 750 kHz (see the datasheet front page). LM20146 will probably still operate, but no specifications are guaranteed in that condition. Why would they want to set the switching frequency below the spec limit?