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TPS7A49:Question About R2 Calculation

Maia Yamakawa
Prodigy 20 points
Part Number: TPS7A49


Tool/software:

Dear team,

I am currently reviewing the TPS7A49 datasheet and have a question regarding the calculation of R2 in the adjustable output configuration.

In equation (2) on page 14, it is written as:

VFB(nom)/R2＞5μA

However, in equation (4) on page 17, the calculation is shown as:

VREF(max)/R2＞5μA

Could you please clarify which voltage—VFB(nom) or VREF(max)—should be used for calculating R2 correctly?

Thank you very much for your help.

Best regards,

Maia

 

  • 0
    TI__Expert 5890 points

    Hi Maia,

    Thank you for asking us!

    VFB(nom) =1.185 is the stricter condition, so it's best to design around equation (2) on page 14.

    The feedback network requirement is mostly to add a minimum load, so the phase margin doesn't become negative (which it happens to be at zero load) over any of the other Recommended Operating Conditions. If you are using an output capacitor that is larger than the minimum recommended 2.2uF this requirement is less strict.

    Best,

    Gregory Thompson