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We have trouble using LM10010+TPS56121 as CVDD of C6678

Jason Gao
Intellectual 720 points
Other Parts Discussed in Thread: TPS56121, LM10010, UCD9222, UCD7242, LM10011

Hi All:

We have a design using LM10010+TPS56121 as the CVDD power supply of C6678,

The reference design is PMP7256.sch from TI website.

But we have two problems when we are debugging the board:


1、The CVDD of C6678 is 1.1V, much higher than design using UCD9222+UCD7242

2、We can connect DSP using XDS560V2,but can not download programs.

   Each time when we download program,error appears:
   "Does not match the target endianness,not loaded. Check project build options
    and target configuration file(ccxml)"

We have double checked the endianness of C6678, it is right just as we were using
UCD9222+UCD7242.

Can you tell me what is wrong with our design?

  • 0
    TI__Guru* 84110 points

    Jason,

    1. CVDD should default to 1.1V at power up. After POR is released, the VID code will be sent out to the LM10010 to set the proper voltage for the CVDD regulator. Please look at the four VCNTL pins to see if they are operating as described in the datasheet and to see what value is being sent out when VCNTL[3] pulses low. The CVDD voltage and VID value will be different from one C6678 device to the next, so you will not expect the exact same value on each board.

    2. There is a boot configuration pin that controls the endianess of the C6678. Once you have connected with the XDS560v2, use the Memory Browser or Watch Window to look at the value of the DEVSTAT register at 0x02620020. What is the value of bit 0? What is that voltage on the LENDIAN pin H25? What is the endianess that your program was compiled to use?

    Regards,
    RandyP

  • 0 in reply to RandyP
    Prodigy 180 points

    Hi RandyP,

          we are facing the same problems as showing.we use the LM10010 and TPS56121 to power the DSPs' CVDD,but the output vlotage is 1.1v,and we have check the VCNTL pins of DSPs.It is exactly different from one C6678 device to the next,and the most important thing is that there are two DSPs  which sent out 111111 through the VCNTL pins,and the output voltage of TPS56121 is 1.125V(not 1.103V as described in page 77 of sprabi2b.pdf ).I am confused  what  can determine the output of the VCNTL pins.

           Meanwhile,Is there some meterial about the Smartreflex!

           Hoping you replay!Thanks very much!!

    Best regards,

    Brian

  • 0 in reply to brian feng
    TI__Guru* 84110 points

    Brian,

    Welcome to the TI E2E forum. I hope you will find many good answers here and in the TI.com documents and in the TI Wiki Pages. I am glad you see you have been searching for the questions others have asked on similar topics. In this case, since this question was marked as Answered, it would usually be better if you post your question to a new thread to get a broader audience who might answer your question.

    It is my understanding that the LM10011 is the correct device to use for the power supply circuit for the Keystone devices. The LM10011 is pin-compatible with the LM10010 but has its logic adjusted for the 1.1V required startup voltage.

    I am not a power supply designer, but I believe that you had to make external adjustments to get the startup voltage of the LM10010 to reach 1.1V instead of 0.9V that other devices required. Those adjustments may have skewed the final voltage as you have seen in your results.

    I apologize that I do not know where to find the examples or the recommended power supply, but you probably have better knowledge of that than I do. If you have a link or a document, please post a link to that.

    Regards,
    RandyP

  • 0 in reply to RandyP
    Prodigy 180 points

    Hi RandyP,

    Thanks very much for your replay and recommandations!

    We designed our borads according to this(http://www.ti.com/lit/ml/snvr131/snvr131.pdf).Do you mean that there is something wrong in the external cricuit of the LM10010 and TPS56121?And because of these wrongs the TPS56121 output the lower initial voltage to make the DSPs output 111111 through the VCNTL pins?

    Thanks a lot！

    Best regards！

    Brian

  • 0 in reply to brian feng
    TI__Guru* 84110 points

    Brian,

    Where did you find a reference to this schematic page, snvr131? I cannot find a reference to it anywhere. It is a valid schematic, of course, but it may not be the right one for this situation, so I would like to help track down the correct information. Your continued help finding this reference is appreciated.

    Regards,
    RandyP

  • 0 in reply to brian feng
    TI__Mastermind 42545 points

    Hi Brain,

    The C6678 will command the voltage needed using the VCNTL lines. The four VCNTL pins should be connected to your LM10010 and should send a sequence once after the C6678 is removed from reset to set the CVDD voltage level. The value sent could be different for every C6678 but many of the parts do request a voltage of 1.1V. Let me ask some specific questions.

    1) Do all of your boards with the LM10010 and the TPS56121 have a CVDD voltage of 1.1V or just some of the boards?

    2) Do you observe an initial voltage of 1.0V which then changes to 1.1V? The initial voltage setting for the LM10010 is 1.0V.

    3) Do you observe the command on the VCNTL pins to set the voltage level to 1.1V? You would see the VCNTL0-2 pins remain high and the VCNTL3 pin toggle once.

    The second issue you mentioned was that a command of 111111 results in a voltage of 1.125V instead of 1.103V. The LM10010 requires very precise resistors to achieve the 5% voltage requirements for the C6678. This is discussed in detail in chapter 3 of the test report (http://www.ti.com/lit/ug/snvu148/snvu148.pdf).

    4) Are you using the 0.1% or 0.5% precision resistors to minimize the voltage feedback error?

    Regards, Bill