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Original question:

LM5117: Design review

LM5117: Design review

JH Shin
Guru 12705 points

Part Number: LM5117
Other Parts Discussed in Thread: CSD19533Q5A

Tool/software:

Hello,

My customer did a circuit review of the LM5117 as shown in the E2E link below.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1336000/lm5117-design-review/5091337

When requesting the above review, the FETs (Q11, Q12) were all CSD19533Q5A. However, while checking TI WEBENCH recently, they found that while Q11 is CSD19533Q5A, Q12 is BSC117N08NS5ATMA1 or BSC037N08NS5ATMA1.

Is it okay to use CSD19533Q5A for both FETs (Q11, Q12)?

Could you please explain the differences with the WEBENCH results?

Thank you.

JH

  • 0
    TI__Guru 68581 points

    Hello JH 

    I think the selected switching frequencies were different between the old and the new WEBENCH results. WEBECH automatically changes the switching frequency based on user inputs. 

    Yes, it is okay to use the new MOSFETs. 

    -EL

  • 0 in reply to EricLee
    Guru 12705 points

    Hello EricLee,

    Thank you for your reply.

    Will there be any problem with the circuit using two CSD19533Q5As previously?

    Regards,

    JH

  • 0 in reply to JH Shin
    TI__Guru 68581 points

    Hello JH 

    I don't have the data, but I don't think there is a problem to drive two  CSD19533Q5As. 

    Please make it sure that '4 pcs MOSFET x Qg x fsw < VCC current limit '

    -EL  

  • 0 in reply to EricLee
    Guru 12705 points

    Hi EricLee,

    EricLee said:

    I don't have the data, but I don't think there is a problem to drive two  CSD19533Q5As. 

    Please make it sure that '4 pcs MOSFET x Qg x fsw < VCC current limit '

    The customer is asking again if you reviewed it correctly.

    They asked if there was a problem with the circuit using only two CSD19533Q5As FETs as shown below in the circuit diagram attached to the previous POST, rather than the case using four of the same FETs.

    The customer's design files attached to the previous post are re-attached below.

    2376.lm5117_20240314.xls

    5001.SCH_LM5117_1.pdf

    Thanks,

    JH

  • 0 in reply to JH Shin
    TI__Guru 68581 points

    Hello JH

    Sorry for the confusion. Please make it sure that 2 pcs MOSFET x Qg x fsw < VCC current limit. I don't think there is a problem for the device to drive two CSD19533Q5As MOSFETs. 

    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