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WEBENCH® Tools/LMR14006: Does Webench Check for minimum on time?

JohnTucker
Guru**** 191445 points
Part Number: LMR14006

Tool/software: WEBENCH® Design Tools

A user tried to design:

I have a few projects running properly with LMR16006Y, using the fixed 3V3 output version.

Trying to confirm a new design today, but Webench does not see it as a valid option for my parameters:

VIN: 9-36VDC
VOUT: 3.3V
Iout: 300mA
Ambient temp: 50oC

I wonder if this device is actually not suitable for that application? It is automotive rated and should be able to deal with 600mA per the datasheet, on an even wider input range...

I replied:

At the maximum input voltage the required on time is less than the specified minimum on time for LMR16006Y.  That is why Webench does not see it as a valid option.

He then tried LMR14006Y:

BUT running Webench for that part, I got surprised to see a "valid" project for the Y version. Here's the Webench link if it helps:
webench.ti.com/.../SDP.cgi

Looking into the datasheet, the min OnTime is even more strict for LMR14006 (table 6.6 shows 95ns).

Now, did I get back to square one on my understanding, or shouldn't webench block this result as well for the same initially posted reason?

Can you look to see if min on time is checked for LM14006Y?

  • 0
    TI__Mastermind 25550 points

    John,

    You are right - there is an issue with the calculation and check for the min on time here. The LMR14006Y has a higher frequency of 2.1MHz and will violate the min on-time spec at 40Vin->3.3Vo (from the shared design). The X version has almost half the frequency of the Y version and might have a better chance at meeting this Vin-> Vo requirement. I will fix the code and let you know once this is released. Thanks for looking at this deeply and notifying the issue to us.

    Regards,

    Amod

  • 0 in reply to Amod Vaze
    Guru 13040 points
    Amod, John,
    Thanks for the attention to the issue.
    I am writing on this post just to "subscribe" to it and receive the future notification as well.
    Regards
    Bruno
  • 0 in reply to Bruno Saraiva
    TI__Mastermind 25550 points
    Bruno, John,

    The min ton check is now added. I see that only a max of 31Vin is working for the 3.3Vo at 600mA and it works only for the LMR14006X which is the 1.1MHz version. For the 2.2MHz version with same design conditions, a max Vin of 16V works in the tool.

    Regards,
    Amod