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LP8732-Q1: About ΔIL

nnn sato
Prodigy 230 points
Part Number: LP8732-Q1

Tool/software:

There are two formulas to calculate ΔIL.

・Formula 2 on page 66 of the datasheet

・Formula 6 from the Application Report SLVA477B, which I was told could be referenced

I would like to use these to substitute into the equation to calculate the inductor value (Equation 5 for SLVA477B).

Why are there two equations to calculate ΔIL?

Which one is correct to use?

How should the two equations be used?

  • 0
    TI__Guru* 81034 points

    Hi Sato,

    The 2 formulas are the same. The datasheet also gives a 2nd formula for calculating the duty cycle. You should follow the datasheet formula for this device.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 230 points

    I think equation 2 on page 66 of the datasheet and equation 6 in the application report for SLVA477B are different equations.
    It appears that you have mistaken it for equation 5 in the application report for SLVA477B.

    According to the equation in the datasheet, the inductor value must be known.
    If I don't know the value, is it correct to think of it as using equations 5 and 6 in the application report for SLVA477B to find it?

    (For example, if I want to find the optimum value depending on the output current value.)

  • 0 in reply to nnn sato
    TI__Guru* 81034 points

    Hi Sato,

    Sorry I was looking at Equation 2 in SLVA477B since this is the equation for ΔIL. Since the datasheet has a recommended inductor value, I assumed you will follow this recommendation.

    Regards,

    Matt