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LM25085: Power management forum

HARINI KRISHNA
Expert 1905 points
Part Number: LM25085
Other Parts Discussed in Thread: BQ24715

Hi,

Hope you are doing good.

A heartfelt thank you to  and    for all the help on the PCB layout 

post: 

The module works fine as expected.

I have few questions regarding the module:

  • we have 2 layer PCB. Can the components be placed at the bottom side of the PCB to reduce the loop size further?
  • The Every time the load is served the inductor gets very hot. is a heat sink required? Can you please suggest on this? i am attaching the data sheet below

    3108.inductor datasheet.pdf

Thank-you

Warm Regards

Harini Krishna

  • 0
    TI__Mastermind 23845 points

    Hi Harini,

    Thanks for the update and the module was able to work fine. 

    As for minimizing the loop, the components can be placed on bottom, just be careful on the sensitive loop such as the Rsense lines as well as the location of CIN in relative to the MOSFET and diodes. 

    For the inductor, what was the switching frequency that you are operating? Also are you using 1.5uH inductor? A part number will help. 

    In general what is the power dissipation on the inductor? 

    Thanks

    -Arief 

  • 0 in reply to Arief Hernadi
    Expert 1905 points

    Hi Arief,

    thank-you for the reply.

    7183.8117.WBDesign6.pdf

    We are following the design from webench .

    The switching frequency is 620.761 kHz  and the power dissipation is 544.0 mW

    The value of the inductor is 1.uH.

    Part number : SMMS1050-1R2M

    Thank-you

    Warm regards

    Harini Krishna

  • 0 in reply to HARINI KRISHNA
    TI__Mastermind 23845 points

    Hi Harini,

    It looks like the inductor should not get too hot. Do you know how hot it gets?

    Also, can you try different inductor brand and see if it helps with thermal?

    You can also try to measure the Switch node and see if the part switch properly and no oscillations seen

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    TI__Mastermind 23845 points

    Hi Harini,

    Due to inactivity, i will close the thread for now. Feel free to open one when you have more questions

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    Expert 1905 points

    Hi Arief,

    hope you are doing good. 

     input to the buck converter reads 12.5V.

    we are observing a condition where the output voltage of the converter falls to  4.77V  when the load current is  1A. 

    We are using bq24715 charger IC through which we connect an adapter which supplies the load when load is present. We have a 6A, 1.625ohm resistive load. . We are following the webench design8156.7183.8117.WBDesign6.pdf 

    Can you please  help us with this?

    Thank-you 

    Warm Regards

    Harini Krishna

  • 0 in reply to HARINI KRISHNA
    TI__Mastermind 23845 points

    Hi Harini,

    Is this a different issue from before or is it the continuation from the previous thread?

    Normally i would check the layout or look at the switching of the converter at the switch node

    Also the point where you measure the output voltage matters to see if the part able to regulate at the correct voltage. 

    Thanks 

    -Arief