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LM5160: Buck power design inquiry

Matt Calvo
Genius 14175 points
Part Number: LM5160

Hey Buck Regulator team,

I have a customer working on a power tree for a new design and we were hoping your team could provide some guidance. Please see a summary of the input/output requirements below in addition to some questions!

We’re attempting to use a flybuck on several designs. Do you have any idea how discontinuous we can run while maintaining stability? All the TI docs and tools say to target 40% ripple (continuous mode), but I’m not sure if that’s controller related or just an arbitrary target based on perceived sweet spot for losses. If it’s controller related, I guess we could increase the load of the non-isolated output as needed. It would be 100% wasted power, but I don’t think we care.

We have 3 output voltage cases to cover. This is a gate drive application with 3 high side windings and 1 for low side. Vin range is approximately 16-20V. Output case 1 is 18V. Output case 2 is 21V. Output case 3 is 25V. These output cases are dependent on the SiC we are using. The total power required is probably around 2-3W.

Does LM5160 with flybuck topology seem appropriate for this?

Is it ok if we choose inductance that is DCM at our typical operating condition? If not, we may have to switch upwards of 1MHz or increase the load on the non-isolated output as needed but would rather not if it isn’t necessary.

Looking forward to your feedback!

Best regards,

Matt Calvo

  • 0
    TI__Guru 74310 points

    Hi Matt,

    Thank you for reaching out.  

    Regarding the 40% ripple current, it is not device related but an empirical consensus that the overall design would be optimized with such ripple current.   

    Please consider the LM5160 or LM5160A should be able to support this application.  You can design with DCM but it is more easily to trigger the current limit at full load.

    You may also consider the LM518x PSR flyback devices. 

    Best Regards,

    Youhao

  • 0 in reply to Youhao Xi
    TI__Genius 14175 points

    Thanks for the feedback Youhao!

    I've passed this info along to the customer and will have them comment back on here directly with any follow-up questions they may have.

    -Matt

  • 0 in reply to Matt Calvo
    TI__Guru 74310 points

    Hi Matt,

    Thank you for promoting our devices.  We will monitor this case in the Forum.

    Best Regards,

    Youhao