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C667x CVDD min/max

Courtney Cooley
Prodigy 235 points

Can you please confirm the min and max recommended operating values for the CVDD voltage? The datasheet gives the following:

CVDD nom: 0.9 - 1.1 V

CVDD min: CVDD-0.05*CVDD

CVDD max: CVDD+0.05*CVDD

To me it seems like the lower threshold of the nominal voltage should be used to calculate CVDD min (so min = 0.855 V), and the upper threshold of the nominal voltage should be used to calculate CVDD max (so max = 1.155 V).

Can you please confirm that my interpretation is correct? If it is not, can you please explain to me what the correct values are?

Thank you very much.

-Courtney

 

  • 0
    TI__Mastermind 30825 points

    Courtney,

    The CVDD is an AVS supply, it will change from device to device.  One device may have it set at 0.9V another device may have it 1.1V.   The nominal range is listed, and but the accuracy must be +/-5% of whatever the programmed fixed value is that comes from the VID values of the Smart Reflex.

    Best Regards,

    Chad

  • 0 in reply to Chad Courtney
    Prodigy 235 points

    Thanks Chad,

    I want to make sure I understand... So in order to verify that I am within spec, I need to know what the programmed fixed value is and then measure the min/max voltage on the rail to make sure I am within 5% of that? And the programmed fixed value is within the nominal range of 0.9V to 1.1V? Should I see the programmed fixed value as the DC average? If not, how do I determine what that value is?

    Thanks.

    -Courtney

  • 0 in reply to Courtney Cooley
    TI__Mastermind 30825 points

    The programmed fixed value comes from the VID (VCNTL) pins to the smart reflex circuits.  There's a couple ways that you could find out what the VCNTL value is, such as reading it from the SR controller, or capturing it as it is accessed.  But there's not a register in the DSP to go read and figure out what it is.  From a design perspective you just need to make sure you're designing it w/ supplies that have this level of accuracy.  TI has digital solutions for this defined and we are working on some lower cost analog solutions as well that should be coming out soon.

    Best Regards,

    Chad

  • 0 in reply to Chad Courtney
    Prodigy 235 points

    Thanks Chad.

    I was able to read the value from the SR controller using the Digital Fusion Power Designer software.

    -Courtney