• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 198 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.

LM5160A: LM5160A

dang xiaofeng
Prodigy 140 points
Part Number: LM5160A

Tool/software:

When we use this IC as flybuck circuit .According to the inductance calculation formula, this should be the maximum value, not the minimum value limit, right?
  • 0
    TI__Guru 50501 points

    Hello Dang 

     Based on the datasheet, you are correct. Please refer the equation 13 in the datasheet. 

    -EL

  • 0 in reply to EricLee
    Prodigy 140 points

    uh? i said that :it's the max value,u said that is the min value,so,who is right?

  • 0 in reply to dang xiaofeng
    TI__Guru 50501 points

    Hello Dang

    Based on the datasheet, it is minimum inductance value. 

    -EL

  • 0 in reply to EricLee
    Prodigy 140 points

    But why is it calculated as 94uH in the DEMO board introduced on the official website, but 60uH is actually selected?
  • 0 in reply to dang xiaofeng
    TI__Guru 50501 points

    Hello Dang

    I am not sure how did you calculate the inductance value in your excel file. 

    Please read the 8.2.1.2.4 section in the datasheet . You can see clearly 26uH is calculated minimum L value and 47uH is selected. 

    Based on Equation 13, determine the minimum value of the inductance as 26 µH for VIN = 65 V (maximum) and
    inductor ripple current equal to 40 percent of the maximum load current. Allowing some margin for inductance
    variation with current, select a higher standard value of L1 (L) = 47 µH for this design.

    I will be out of office and I will not be able to reply this E2E post anymore.
    If you are still trying to resolve the issue, please don't reply on this post, but create a NEW post to get a help from other engineers quickly.
    -EL

  • 0 in reply to EricLee
    Prodigy 140 points
    The excel file I attached is the DEMO board calculation book on your official website, not the one I calculated myself.
  • 0 in reply to dang xiaofeng
    TI__Guru 74310 points

    Hi Xiaofeng,

    Eric is ooo, so let me try to answer you.  The min inductance calculation in design calculator uses the same equation of the datasheet, in which the desired ripple current is set to 40%.  Our design calculator is intended to help the users to get a good start point.

    The 20 to 40% ripple current is an empirical understanding to get an overall optimal design, but it is not an absolute requirement. Theoretically the circuit should work with any inductance, but the other components selections may become difficult or even prohibitive. The users can also choose a transformer readily available even if it slightly deviates from the calculator's recommended values.  This is why we leave the final decision to the users.  At the end, the users should always verify the performance by experiment.

    Coming back to your specific issue:  by choosing 60uH, the ripple current would be about 60%, and it should still work. 

    Hope this clarifies.

    Thanks,

    Youhao