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LMR51410: Want to make an inverting power supply

Ryu Yamashita
Genius 3685 points
Part Number: LMR51410

Tool/software:

Hi team,

I want to make a 17V to -17V inverting power supply with LMR51410.
I am planning to design it with reference to this document, but are there any precautions I should take?
https://www.ti.com/lit/an/slva458b/slva458b.pdf

For example, is there any risk of the positive power supply being output for a moment?

Best Regards,
Ryu.

  • +1
    TI__Mastermind 31185 points

    Hi Ryu,

    Main precaution to keep in mind is the device limits. Usualy we do not expect the positive power supply becoming an output.

    You may refer to this app note also for reference. 

    Thanks,

    Richard

  • 0 in reply to Richard Fu22
    Genius 3685 points

    Hi Richard,

    I have assembled a schematic diagram based on the material.
    Could you please check if everything is OK?

    Best Regards,
    Ryu.

  • +1 in reply to Ryu Yamashita
    TI__Mastermind 24115 points

    Hi Ryu,

    TI recommends that capacitors are rated for at least 2x the voltages they are set to experience to avoid significant de-rating. The input capacitor, bypass capacitor, and output capacitor ratings will need to be increased to avoid this de-rating.

    When using an IBB, the current stresses that the part will experience are higher than what can be expected from the buck operating with its standard configuration. Due to this, the inductor saturation current rating may be insufficient for this application. Please see section 4.2 of the application note richard linked for more details and ensure that your inductor current rating is higher than the Ipeak specification. Section 5.1 also gives some more insight on this selection.

    A diode may be recommended as an output clamp to help with startup. Please see section 7.4 of the application note for more details on this as well.

    Thank you,

    Joshua Austria

  • 0 in reply to Joshua Austria
    Genius 3685 points

    Hi Joshua,

    Thanks for the reply.
    I will refer to it.
    Are you saying that there was no problem with the constants and composition?

    Best Regards,
    Ryu.

  • +1 in reply to Ryu Yamashita
    TI__Mastermind 24115 points

    Hi Ryu,

    I raised the concerns about the input, bypass, and output capacitors as well as the inductor as their ratings were insufficient. However the component values themselves looked to be ok, if they had the appropriate ratings. If these issues are resolved, the application looks like it should work.

    Thank you,

    Joshua Austria