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LM5020: Question about soft start function

Satoshi
Guru 19645 points
Part Number: LM5020
Other Parts Discussed in Thread: LM5021

Please let me know about four points below of soft start function for LM5020.

①LM5020 datasheet is not described Vss_ocv. Is this spec the same as LM5021?

②I think that Vss_off is mean accuracy of Vss_ocv, is it correct? 

③Is there equation of Ton time?

　I found Toff equation, but turn on time is not found.

④I understand that during soft start time make limitation for Comp voltage.

　Is there limit for Duty cycle (~%)?

Best regards,

Satoshi

  • 0
    TI__Guru* 78440 points
    Some answers to your questions:

    (1) It is similar but not characterized. So we cannot say the spec is the same.
    (2) No, it is not correct. Vss_off is dc offset voltage from SS to COMP when COMP is clamped by SS.
    (3) What Ton and Toff are you talking about? In the LM5020 datasheet there isn't Toff equation.
    (4) Yes its purpose is to limit the duty cycle. Wish SS voltage rising the duty cycle gradually increases. Since this is a current mode controller, there are many factors determines the duty cycle including the input voltage, power inductor, and so on.

    Hope these clarify.
  • 0 in reply to Youhao Xi
    Guru 19645 points
    Youhao Xi-san

    Thank you for reply,

    About answer (3), I looked not LM5020 but LM5021 datasheet, sorry for mistake.
    Is there Ton equation for LM502x series?

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Guru* 78440 points
    sorry there is not an equation for Ton.