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LMR14203 / LMR14206 in WEBENCH

Andy Sifferman
Prodigy 20 points
Other Parts Discussed in Thread: LMR14203, LMR14206

Hi, I've been looking at the LMR14203 and LMR14206 for my application.

Input requirements: +8.4 to +32 V

Output requirements: 3.3V @600mA, and 7.0V @100mA

Environmental: -20 to + 70C

I was thinking to use the LMR14203 for the 7V supply, and the LMR14206 for the 3.3V supply.  When I run the on-line WEBENCH tool and enter the above parameters, the LMR14203/LMR14206 are not shown in the results list.  When I click on "Show Why Other Parts Were Not Found" and scroll down to the LMR14203/LMR14206, the comment column reads "Failed Minimum Ton".

What the heck does "Failed Minimum Ton" mean, and is it a valid reason not to use these parts in my design?

Thank you,

Andy Sifferman

  • 0
    TI__Expert 3950 points

    Hello Andy,

    the required minimum on time (at 32V input) of your application is lower than the minimum on time guaranteed from the part.

    For example:

    When VIN = 32V and VOUT = 3.3V the duty cycle is about 10% and since the switching frequency is 1.5MHz (max):

    ton = 67ns

    the LMR14206 has 100ns of minimum on time.

    Reducing the maximum input voltage will increase the minimum required on time and so you can use the parts.

    I hope that asnwer your question.

    Regards,

    Giuseppe

  • 0 in reply to Giuseppe Pinto
    Prodigy 20 points

    Thank you for the very clear and thorough explanation.