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LM62014 - output voltage problem

Oscar Terron1
Prodigy 230 points
Other Parts Discussed in Thread: LMR62014

Hello,

I have a circuit based on the LMR62014 to generate +15 V from a +5 V (+-0,5V) supply, using the component list suggested by the datasheet and by webench. This circuit works fine up to 250 mA.

However, when I try to supply a 300 mA load, the output voltage has some strange behavior. It goes from +15 to +5 V for 10 ms. This behavior is periodic and is repeated every 96 ms. The output voltage capture can be seen on the attachment.  

What can be causing the "shutdown" of the output?

Best regards,

Oscar

  • 0
    TI__Genius 16025 points

    Hi Oscar,

    Please provide a schematic and layout for your design. My guess is either your inductor is not the correct rating or your diode is underrated. Please verify your design with the design schematic below. I am assuming 300mA is your target Output current. Just FYI, this IC can only provide up to 525mA of output current for a 5V in to 15 Vout.

    0003.[E2E]Boost Converter - Oscar.pdf

    Thanks,

    Anston 

  • 0 in reply to Anston Lobo
    Prodigy 230 points

    Dear Anston,

    The component list that I used was based on the webench tool, for a Vin of 4.5 to 6 V, Vout=15V, Iout=0.4 A.

    The only difference is that in my case, the inductor is the Bourns SRN6045-100M (10 uH). The diode is the same.

    This difference in the inductor may cause this strange behavior related with periodic output shutdown? 

    Best regards,

    Oscar

  • 0 in reply to Oscar Terron1
    TI__Genius 16025 points

    Hi Oscar,

    The inductor you've chosen is fine. Can I see your layout?

    Thanks,

    Anston

  • 0 in reply to Anston Lobo
    Prodigy 230 points

    Dear Anston,

    the layout is included in the attachment. Do you think that a not so good layout can trigger some LMR62014 internal protection, resulting in the  "shutdown" of the output?  

    Best regards,

    Oscar

  • 0 in reply to Oscar Terron1
    TI__Genius 16025 points

    Hi Oscar,

    There are extra components in your layout that don't match the Webench schematic. Can you provide the schematic that goes with this design showing the component identification? Also, please zoom out a little more so I can see the full layout of the part.

    The periodic shutdown of the part looks to be thermal shutdown. Are you operating this part in high ambient operating temperatures or some other thermally insulated environment?

    Another suggestion, sense the current on the inductor by placing a loop from the Switch end of the inductor to the Switch node and ensure that it is 300mA and not higher.

    Thanks,

    Anston