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TPS54325 - improve thermal issue

Knighty Nimp
Expert 1260 points
Other Parts Discussed in Thread: TPS54325, TPS54320, TPS54620

Hi,

We facing temperature issue(high temp) on IC controller in current design. Anyone give idea how to improve thermal of IC controller(integrate switch) in general syncronouse buck concept design.

Thanks,

NT

 

  • 0
    TI__Guru**** 191445 points

    What IC?  You should always include the device number in the title of your posts.  What design specs?

  • 0 in reply to JohnTucker
    Expert 1260 points

     

    TPS54325,  we just only to improve only temperature on IC controller.

    Vin: 11 - 16

    Vout: 5V

    Io: 3A

    NT

  • 0 in reply to Knighty Nimp
    Expert 1260 points

    Or any new controller(use for same spec as below) which can be better in term of disipate thermal?

    ======================================

    TPS54325,  we just only to improve only temperature on IC controller.

    Vin: 11 - 16

    Vout: 5V

    Io: 3A

    =====================================

    NT

  • 0 in reply to Knighty Nimp
    TI__Guru**** 150880 points

    The TPS54325 is already in a pretty big package with a thermal pad, so you should be able to keep it cool with a good layout.  Can you post your board layout?  What temperature do you need to keep it below and at what ambient temperature?

    There are 2 ways to reduce the operating temperature--reduce the power loss and/or reduce the thermal impedance to the ambient.

    To reduce the power loss, you would have to switch to a different part.  The TPS54320 has lower Rdson FETs and has a programmable switching frequency.  The lower Rdson FETs will reduce the full load power loss while lowering the frequency will reduce the loss at all loads.  And even more efficient part would be the TPS54620 with its even lower Rdson FETs.

    To reduce the thermal impedance, you need to increase the amount of copper connected to the thermal pad.  Use vias under the part to connect the top copper to all board layers.  Make this ground plane as big as you can.

    ti.com/thermal has lots more information.  I encourage you to browse around there.

  • 0 in reply to Chris Glaser
    Expert 1260 points

    Chris,

    Thanks, if the input voltage drop down to 8.5V (typ) and output is 5V/3A. duty is about 58.8% so how to choose internal switch(especilly Rds_on) for both high side and low side.

    Or any application note describe on this selection?

    NT

  • 0 in reply to Knighty Nimp
    TI__Guru**** 150880 points

    Ideally, you would want the power lost in each FET to be the same.  So, you would want fairly equal Rdsons.  But you want to do that at your typical Vin condition, not worst case.  Also, note that the duty cycle will increase beyond ideally Vout/Vin as the converter overcomes losses.

    But this isn't as important as getting the maximum efficiency.  All of our parts have efficiency graphs.  You just need to pick an acceptable/the best efficiency.

    I am not aware of an app note on this topic