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LM3409HV: No Control Loop Compensation Required and PWM switching frequency

Hirotaka Matsumoto
Guru 27585 points
Part Number: LM3409HV

Hi all

Would you mind if we ask LM3409HV?

<Question1>
Why is this device "No Control Loop Compensation Required"?
Does this device have internal phase compensation circuit?
Or, because of comparator feed back like as COT??

<Question2>
The switching frequency varies regardless of constant current operation.(like as 170KHz, 150KHz.)
We assume that there is no ocillator in this device.
So, we guess that it depend on "On time".
The actual frequency may vary quite a bit.
Is our recogniton correct?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Mastermind 25500 points

    Hello Hirotaka-san,

    That is correct, it is constant off time hysteretic so it is inherently stable and very high bandwidth so no compensation is required.

    Since it is constant off time the switching frequency can very a bit over input voltage changes. It will vary less with variations in output voltage, but it still will some. Hysteretic control has many high performance and ease of use benefits, but it doesn't give constant switching frequency.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Guru 27585 points

    Clint san

    Thank you so much for your reply!
    OK, we got it.

    Kind regards,

    Hirotaka Matsumoto