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LM5022: Rsns equation(36) and selected value

Shinichi Inoue
Guru 21556 points
Part Number: LM5022

Dear Specialists,

My customer is considering LM5022 and has a question.

I would be grateful if you could advise.

---

I am confirming LM5022 datasheet P.21 Rsns equation(36)

I solved this, the result is 0.0676.

I think closet value is 68mohm, but selected 100mohm, although there are several resistances up to 100mohm.

I'd like to know why 100mohm is selected.

Plus I don't know the meaning of tripling in the equqtion(36) of (Vo - Vin) x 3 x D.

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Guru* 78060 points
    There is another E2E thread in which Garrett presented the derivation of these equations, and explained the why 3x is introduced. Designers usually use K>1 for margins. These equations just give you a guideline and you can select 68mOhm but 100mOhm might be an more available part when the designer of the example circuit was selecting parts. With different Rsns, you may need to adjust Rs1 and Rs2 in accordance.

    Please check the following link so I don't need to duplicate here.

    e2e.ti.com/.../653822

    Thanks
  • 0 in reply to Youhao Xi
    Guru 21556 points
    Hi Youhao,

    Thank you for your reply.

    I'll share your advice with the customer.

    If he has an additional question, I consult you again.

    I appreciate your great help.

    Best regrads,
    Shinichi