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TPS563208: Do not allow switching current to flow under the device

Nir Flysher
Expert 3287 points
Part Number: TPS563208
Other Parts Discussed in Thread: TPS565201

Dear Team,

My customer would like to the TPS563208 and sent in the following question :

In the datasheet, page 17, in the layout guidelines section, it is stated that “Do not allow switching current to flow under the device”.

What is the reason for this recommendation?

Is it going to cause EMI issues? Or it is going to disturb the stability of the buck? Or something else?

Can you please clarify this comment ?

Regards,

Nir.

  • 0
    TI__Genius 13451 points

    Hi Nir!

    It is possible to disturb the normal operation of the device. Because switching current or switching node have high di/dt or dv/dt behavior, it is easy to couple noise into device if it is close to device.

    Shuai

  • 0 in reply to Shuai Fan
    Prodigy 10 points

    Thank you for your fast reply!

    In my current layout the switching current placed under the component (caused by a layout constraint).
    During the tests the output voltage is stable and I cant see any problem with the stability of the output.

    I am afraid that I am missing something, what can be the consequences of the noise coupling?
    Can it (the noise coupling) cause more power dissipation? lower efficiency? EMI problems? or it is only related to the stability of the buck?
    I am trying to understand whether my "not recommended" layout caused some problems, and if yes how can I identify/quantify them.

    thank you again,

    Slava

  • 0 in reply to Slava Frosinsky
    TI__Genius 13451 points

    Hi Slava!

    As there exists parasitic capacitor between SW copper and IC's internal electrical node. If you put SW node under the device, this parasitic capacitance will be large, there will be a noise current C*du/dt couple into IC and interfere its internal signal level.

    I will cause any power dissipation or efficiency issue.

    You can refer the layout of TPS565201 which is P2P with TPS563208.

    https://www.ti.com/lit/pdf/slvub70

    Shuai