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LM5001-Q1's reference circuit of SEPIC

Other Parts Discussed in Thread: PMP9481, LM5001-Q1

Dear all,

I compare LM5001-Q1's datasheet page.17 with PMP9481 schematic.

I would like to know the difference LM5001-Q1's datasheet and PMP9481.

Relative to LM5001-Q1's datasheet, PMP9481 schematic has more parts.

I would like to know the role of these additional parts.

(PMP9481's schematic URL → http://www.ti.com/lit/df/tidran4/tidran4.pdf)

Q1. about C2 and C5

What is the purpose of these constant?

Why are these set parallel?

Q2. about R1

What is this function?

What is the purpose of this constant?

Q3.about R3 and C1

What are these function?

What are the purpose of these constant?

Q4. about R6

Is this resistor's purpose evaluation of phase margin?

Q5. about CX1/CX2/CX3

What are the purpose of these?

Q6. about L1

I think that this spec(470µH/1.6A) is pretty big.

I would like to know the design reason why this inductor is set this constant.

Q7. about C7 and C8

What are these function?

What are the purpose of these constant?

Best regards,

  • Q1. about C2 and C5
    Answer: They are input capacitors, which are connected in parallel to achieve larger capacitance

    Q2. about R1

    Answer: R1 and C3 together are used as high frequency filter

    Q3.about R3 and C1

    Answer: It is RC snubber to damp voltage ringing

    Q4. about R6
    Answer: Yes, it is used for loop gain test

    Q5. about CX1/CX2/CX3
    Answer: They are part of EMI filter

    Q6. about L1
    Answer: It is part of EMI filter, it is not part of power conversion stage.

    Q7. about C7 and C8

    Answer: EMI filter.