• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 82 subscribers
  • Views 220 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28P550SJ: Use XTAL_OSC_SE in hardware, but configure XTAL_OSC in software, F28P55 can work, is there any risk?

Zane Wei
Intellectual 1965 points

Part Number: TMS320F28P550SJ

Hi Team,

Here is schematic of F28P55 clock:

 

image.png

image.png

We can see customer is using single-end mode. But customer configure it as dual-end mode:

It should be XTAL_OSC_SE, but customer configure it as XTAL_OSC, the device can work normal, and they can see CLK_OUT(20MHz) on GPIO18(X2). Customer product have MPed, so it not easy to modify their program, they want to know it will have some risk for their product? If not, GPIO18 output 20MHz clock will increase system power? Thanks!

image.png

image.png

image.png

  • 0
    TI__Mastermind 43520 points

    Hi Zane,

    The risk is that, instead of the Pierce Oscillator circuit being off in SE mode, it is now always on.  Customer probably needs to quantify how much power is consumed by the oscillator being on by running with XTAL config and with XTAL_SE on the production board and ensure that the difference is not over 1mW.  Output X2 is open so there should not be any load in XTAL config but good to check.

    Regards,

    Joseph  

  • 0 in reply to Joseph Casuga
    TI__Intellectual 1965 points

    Hi Joseph,

    Thanks for your reply. I want to know if customer can't change to SE mode in their product. It will have some risk cause device can't work?

  • 0 in reply to Zane Wei
    TI__Mastermind 43520 points

    Hi Zane,

    There probably is a long term effect of the xtal oscillator turning on/trying to start up when it is in SE mode.  Since this is not a typical use case, it was not factored in on the overall device performance so as such, this will already be a risk.  Best to advise customer to change FW the first chance they can,

    Regards,

    Joseph

  • 0 in reply to Joseph Casuga
    TI__Intellectual 1965 points

    Hi Joseph,

    Thanks for your quickly reply. Now customer have deliver their product to end customer. It very hard to modify the software. They have boot loader and application, after bootrom, it will entry bootloader first, then jump to APP. Now they found if only change the right CLOCK setting in APP, it can't stop X2 output 20MHz. Cloud you help check with design team about how the internal clock work? this maybe help understand this issue. Thanks!

    Best Regards,

    Zane

  • 0 in reply to Zane Wei
    TI__Mastermind 43520 points

    Hi Zane,

    Can you provide more details below:

    Zane Wei said:
    Now they found if only change the right CLOCK setting in APP, it can't stop X2 output 20MHz.

    Thanks,

    Joseph