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UC3843: Does UC3843 have a limit of minimal DUTY?

Ronald Wang
Intellectual 390 points
Part Number: UC3843
Other Parts Discussed in Thread: UCC38C43

Dear TI,

In the 3843's Datasheet, the minimum duty is 0%. Does the 3843 have problems that cannot be overcome if the Duty is set to a minimum (eg, 0.01%)?

Thank you！

Best regards,

Ronald

  • 0
    TI__Mastermind 34465 points
    Hello Ronald,
    This part has a maximum switching frequency of 500kHz and the minimum duty cycle you can obtain is related to the switching frequency you are using. Pulse widths lower than this cause the UC3843 to start missing switching cycles and you get times where the converter goes into a burst mode.
    You should be able to get a minimum pulse width of 200nS. At 100kHz this gives Dmin = 1% and at 20kHz Dmin = 0.5%
    The UCC38C43 is an equivalent part with a faster oscillator.
    Regards
    John
  • 0 in reply to John Griffin1
    Intellectual 390 points
    Hi John
    Thank you for your help

    Regards
    Ronald