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TPS53659: TPS53659 bode plot question for VPP

user1874945
Intellectual 300 points
Part Number: TPS53659
Other Parts Discussed in Thread: TPS53679,

Hi TI Expert,

Per 'TPS53679_59 Schematic and PCB Review GUIDE_Rev10' page 13, there is below sentence for VPP. May I ask why adding 2x100ohm local sense can help to improve the bode plot?

VPP voltage needs a 453/124ohm resistor divider and set Vboot to 2.29V to avoid being at the top of the DAC range. Recommend add 2x100ohm local sense to improve bode plot.

Thanks,

Dora

  • 0
    TI__Expert 5830 points
    Hi Dora,
    Thanks for the question. Improve bode plot here means to have more phase margin compared to only 124ohm//1kohm resistor divider on BVSP/BVSN. As TPS53659 rail B mostly used for VPP which is single phase rail with limited copper and the huge distance from inductor to the output load, it leads to higher parasitic inductance from PCB into the loop.

    There is a detailed diagram in the review guide, which is 124ohm series resistor to remote sense and 100ohm series resistor to local sense connect together back to pin 28 (BVSP), by this way, controller can see Vout from local side and Vout from remote side at the same time but get higher phase margin due to less parasitic inductance from local side then result in higher phase margin.

    Hope this answer your question.
    Thanks
    Chasel