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LM10011: Power circuit for CVDD to C6654

Ramgopal Divakar
Expert 1300 points
Part Number: LM10011
Other Parts Discussed in Thread: TMS320C6654, , TPS53681, TPS54521

Hi!

I am working on a new design with DSP TMS320C6654. Is there an evaluation circuit to power CVDD?

The hardware design guide recommends LM10011 with a keystone I device which is C6654 in my case. I would like to use a circuit if it already exists. Specifically a DC-DC. Assume my input voltage is 12V.

It looks like I would need around 3A at the output

  • 0
    TI__Guru**** 191445 points

    Ramgopal,

    TMS320C6654 requires multiple voltage rails for operation.  Only one of these, CVDD, needs to be adjustable via SmartReflex.  The hardware guide recommends UCC9244 which is superseded by TPS53681.  LM10011 is a general purpose digital voltage scaling current DAC.  It can be used with any dc/dc converter that meets your input voltage, output voltage and output current requirements, which you have not specified.  Since you placed LM10011 as the part number, your post was placed in this forum.  We can help you with specific dc/dc converter questions.  Please provide your input voltage, output voltage ( It is likely 0.9 V +/- 0.1 V for CVDD) and required current.  That said, it looks like you will need additional support for your TMS320C6654 project.  You are likely better off to post specifically to the Processors Forum using TMS320C6654 as the part number for assistance.  If you have specific DC/DC converter questions please feel free to post back here for help.

  • 0 in reply to JohnTucker
    Expert 1300 points
    John,
    thanks for the quick response. I looked at the evaluation board listed under C6654 which was a C6657 IC and it did use the UCC9244 but that is not recommended for new designs like you state above. I do see UCC9244-EP as an active part. But that doesn't look straight forward as I have to program the device on power up. I will look into it.

    In the meantime.

    Let us assume I will the LM10011 with the DSP C6654. I need a DC-DC to provide 0.85V-1.1V CVDD output that will also work with LM10011 to provide variable output depending on the DSP needs. The current estimate is 3A so a 5A circuit as shown here would work for me. Input supply is 12V from our back plane.

    Is this something I can use? PMP8275 application schematic:

    www.ti.com/.../tidr731.pdf

    If this would work, then one question I had is why is there a feed back from the output via R7, R6, R9 divider circuit back to the VSENSE pin 7 of the controller? Is that meant to be DNI? I thought the output is controlled via LM10011?
  • 0 in reply to Ramgopal Divakar
    Expert 1300 points
    For David Baba to the question posed below:

    1. Ease of solution
    2. Size
    3. Efficiency
    4. Cost

    David Baba replied to LM10011: Power circuit for CVDD to C6654.

    Hello Ramgopal,

    Can you kindly share what output voltage you need? Also please can you share your design criteria for your system? High efficiency, size, cost, ease of use solution ?

    Please can you rank the above to give me some idea of the kind of solution you are looking for?

    Thanks.

    Kind Regards,

    David Baba.
  • 0 in reply to Ramgopal Divakar
    TI__Guru**** 191445 points
    Ramgopal,

    You still meed the basic feedback for LM10011. For voltage margining the LM10011 injects current into the FB node. The more current that is injected into the FB node by the LM10011, the lower the output voltage will be. For non-margining operation:

    Vout = Vref *((Rtop/Rbot) + 1)

    When adding in the LM10011 margining circuit;

    Vout = Vref *((Rtop/Rbot) + 1) - (Idac *R1)

    Where Idac is the programmed output current of the LM10011.

    That reference design PMP8275 is specifically intended for these type applications. It should work for you as shown in the schematic.
  • 0 in reply to JohnTucker
    Expert 1300 points
    Oh okay,
    I didn't realize Vsense was the FB pin. Makes sense.
    Do you have a BOM for PM82875 and a document? I assume this is a part of some eval board?
    Also, how can I get my schematics checked when done just to be sure?
    This is a good solution as C6654 is not a high end DSP and the current is not much unlike C6778 where it can go to 8A.
    Thanks a lot for the quick response,
    Divakar
  • 0 in reply to Ramgopal Divakar
    TI__Guru**** 191445 points
    Ramgopal,

    You can down load the design files here:
    www.ti.com/.../tidep0011
    TPS54521 dc/dc converter is supported by our MCP team. If you post your schematic and place TPS54521 in the part number field, someone will review it. If you follow the PMP8275 design exactly, you should be good. That design was built and tested. You can get the test report at the same page above.