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LMR36520: Layout guideline

Michiaki Tanii
Expert 4580 points
Part Number: LMR36520

Hi team,

 

Could you kindly advise the layout as following.

 

- Customer would like to know how to choose CHF in terms of frequency characteristic.

- Why is GND placed under inductor in the layout example ?

   In their understanding, GND under inductor is not placed to avoid the noise.

 

- Could you provide the recommendation of GND plane at internal layer and bottom plane ?

 

Thank you and best regards,

Michiaki

  • 0
    TI__Mastermind 35170 points

    Q1: 100nF to 470nF would be good, based on experience.

    Try to choose smallest package size to minimize ESL, ie: 0402,0603.

    Q2: There are some different opionions wether or not to have ground between inductor terminals. 

    Based on my experience and research, I perfer ground under the inductor.

    Q3: Please see recommended layout near the end of the datasheet.

  • 0 in reply to Marshall_Beck
    TI__Expert 4580 points

    Hi Beck,

     

    Why do you prefer ground under inductor ?

     

    For example, a competitor mentioned that the GND should not be placed under inductor since it caused reduction of inductance or increasing loss by eddy current in GND.

     

    Please let me know what benefit and intention GND is placed under inductor.

     

    Thank you and best regards,

    Michiaki

  • 0 in reply to Michiaki Tanii
    TI__Mastermind 35170 points

    I viewed as it a means to capture radiated efield. 

    I have also viewed articles with counter arguments.

    My personal preference is to have it that way, as I have gotten good EMI performance with my board design with that design practice.