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TPS92200: Deviation of max Duty

Yutaka Horie
Prodigy 20 points
Part Number: TPS92200


Tool/software:

Dear TI engineers,

I would like to know how much voltage can be output when Vin is 10.8V in the worst case consideing deviation.
In the section 6.6 of dataseet, I can see that Max duty cycle is defined as 99%. But 99% is only typical value and there is no description on Min value.
I think it can be calculated by using the maximum value of tMIN_OFF and the minimum value of tMAX_ON if both value have independent deviation(in the case if both value have proportional relation, the worst ratio of  both value can be used).

Best regards,

YTK

  • 0
    TI__Intellectual 1860 points

    Hi Yutaka, 

    Glad to help you! 

    Actually, the ton/toff time are not related to max duty. If using normal design, max duty cannot reach 99%. In TPS92200, frequency will automatically expand the switching  frequency to reach a VOUT very close to VIN. So, the EC table only shows 99%. 

    Could you please share your end equipment application and run rate please? 

    Thank you! 

    Best, 

    John. 

  • 0
    Prodigy 20 points

    Hi John,

    Thanks for your reply.
    I understand TPS92200 can automatically expand the switching frequency by expanding the on tme in the case if VOUT becomes very close to VIN.
    But 99% on duty is calculated by using tMAX_ON(typ 6.6us) and tMIN_OFF(typ 65ns), right? 6.6us/(6.6us+65ns) x 100 = 99[%]
    If this is correct, the minimum value of  Max duty cycle is calculated by using the maximum value of tMIN_OFF and the minimum value of tMAX_ON if both value have independent deviation(in the case if both value have proportional relation, the worst ratio of  both value can be used).
    Anyway, I want to know how much On duty is guaranteed considering various deviation of electrical characteristics of TPS92200.
    Would you please let me know how much on duty is guaranteed? If it is 99%, I would be happy.

    Thanks and best regards,
    YTK

  • 0 in reply to Yutaka Horie
    TI__Mastermind 35560 points

    Hi YTK,

    We will give you reply later.

  • +1 in reply to Yutaka Horie
    TI__Intellectual 1860 points

    Hi Yutaka, 

    I have checked with our design team. The have provided the min value of max duty, 98.5%. It is calculated by max on and min off like you mentioned. 

    Could you please share the EE please? We really want to understand why this application have VOUT so closed to VIN.

    Thank you! 

    Best, 

    John! 

  • 0 in reply to John Shen
    Prodigy 20 points

    Hi John,

    Thanks for your reply. I really appreciate it.
    Regarding end equipment, I can't tell you what kind of product we would release right now, since this is a feasibility study of LED drive circuit for future products.

    Thanks and best regards,
    YTK

  • 0 in reply to Yutaka Horie
    TI__Intellectual 1860 points

    Hi Yutaka, 

    Got it! Thanks for reaching out to us again!

    Best, 

    John.