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TI Home » TI E2E Community » Support Forums » Clocks & Timers » Clocks & Timers Forum » LMX2487E, fractional numerator and denominator
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LMX2487E, fractional numerator and denominator

This question is not answered
S.Satoshi
Posted by S.Satoshi
on Apr 10 2012 23:22 PM
Genius3085 points
LMX2487E can be set fractional numerator and denominator from 0 to 4194303 individually.
Then how will LMX2487E behave if fractional numerator and denominator will be set to 0 in the wrong ?
In that situation, they look like to set to 1 each automatically, not 0 at customer's evaluation.
Please give your comments if this guess is correct.
Best Regards,
PLL
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  • Dean Banerjee
    Posted by Dean Banerjee
    on Apr 11 2012 17:11 PM
    Intellectual2840 points

    Technically, a fraction with denominator 0 is undefined and therefore you should not do this.  Fractions like "0/0" are undefined.

     In the LMX2487E, I know that this will actually work with a fractional denominator of 0.   I though that it ignored the fraction in this case but it might be the case that

    it adds 1 to the N value.  For our codeloader software, a '0' denominator would originally cause this to crash, but we modified the software to handle this error case.

    In summary, you should not program the denominator to zero and there is no benefit or application where it would make sense to do so.  We do not test in this mode.

    But for the purposes of satisfying your curiosity, the part will actually function and lock with this condition -- even though we do not recommend this.

    LMX2487E
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  • S.Satoshi
    Posted by S.Satoshi
    on Apr 12 2012 00:12 AM
    Genius3085 points

    Hi Banerjee-san,

    Thank you for your quick and detailed answer. I understand that the LMX2487E will function and lock with denominator 0, but I do not recommend customer to use with this condition.

    Best Regards,

    S.Satoshi

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