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LMR38015: Inductor selection with wide Iout range

Frank H
Intellectual 2660 points
Part Number: LMR38015

Tool/software:

Team,

Can you please help with the inductor selection for the following circuit conditions?

V IN: 14….72V.

V OUT: 12V.

I OUT: 0.05A….1.0A

The challenge is the short-circuit current of the LMR38015. Maybe we can mitigate it with the following inductor, which has a soft saturation curve.

WE-MAPI SMT-Speicherdrossel | Passive Bauelemente | Würth Elektronik Produktkatalog (we-online.com)

What do you think?

 

It seems that the simulation under 1A is not working, but I suspect that with an acceptable ripple we have to go toward 33 or even 47µH and away from the 10µH that we simulated with the higher currents.

 

Here some questions:

  1. What is the difference between the different derivatives with and without Q1?
  2. How do I connect and simulate circuits for output currents of approx. 200 to 500mA?
    • So far, whenever we try to simulate, the simulation breaks off with incomprehensible information
  3. Is this switching regulator right for us?
  4. Which frequency is recommended for small inductor sizes? 1MHz ?
  5. Is it possible to operate from 100mA to 0.7mA?

Thanks a lot!

  • 0
    TI__Guru* 76965 points

    Hi Winnie,

    Thank you for posting.  Sorry currently the expert of this device is out of office.  I have notified him so he will respond after he returns work.

    Best Regards,

    Youhao

  • 0
    TI__Mastermind 28460 points

    Hi Winnie:

    1) Q1 refers to the automotive-grade of the part. So a device with -Q1 at the end means that part is suitable for automotive applications, and a device without it means it is not suitable for automotive applications.

    2) What is your switching frequency and what are you simulating with?

    3) It looks like this device can support the application requirements.

    4) Usually, for small inductor values, you would want to switch at high frequencies, like 2.1MHz.

    5) Yes, this would go to no-load operation. The LMR38015 should have FPWM operation (which shows CCM operation, even at light load).

    Thanks,

    Richard