• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 82 subscribers
  • Views 513 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.

TMS320F280049: PMBus at 1MHz (Fast Mode+)

Wayne Huang
Genius 16825 points

Part Number: TMS320F280049

Dear Champs,

I am asking this for our customer.

They will need PMBus at 1MHz.

On F280049 datasheet, Sec 5.12.3, it says

http://www.ti.com/lit/ds/symlink/tms320f280049.pdf

"Fast Mode+: 1000 kHz. This mode applies only to the PMBus module operating in I2C mode, with an input clock frequency of 20 MHz."

Would you please explain this in more detail?

1) Can this PMBus module support Fast Mode+ at 1MHz?

2) What does that mean by "in I2C mode"?

3) Is there any restriction or condition when using it at 1MHz?

Wayne Huang

  • 0
    TI__Guru 55700 points

    Wayne,

    PMBus specs v1.0 / v1.1 supports only 100KHz and 400 KHz.

    Is the customer trying PMBus as a I2C? I believe we have had this discussion in the past that I2C mode available in PMBus comes with its limitation and is not a full-blown I2C containing all the features of C28x I2C. There has been some recent efforts to support PMBus talking to EEPROM in I2C mode in master transmit / receiver mode until 400 KHz. Next release of the datasheet has the 1MHz I2C mode removed.

    How is the customer planning to use PMBus peripheral?

    Regards,

    Manoj

  • 0 in reply to Manoj Santha Mohan
    TI__Genius 16825 points

    Dear Manoj,

    The customer is thinking if it is possible to support PMBus1.3/SMBus 3.0 by F28004x PMBus module.

    That is,

    1) by adding external level shift for DC level change (for SMBus 3.0)

    2) by software on top of the PMBus module

    3) by 1MHz PMBus module.

    If they can deal with 1) and 2), is it possible to support up to PMBus 1.3? 

    Because there is such description, they are interested and wonder this.

    Wayne Huang

  • 0 in reply to Wayne Huang
    TI__Guru 55700 points

    Huang,

    I don't think we can get PMBus1.3 working using PMBus available in F280049. But, let me check and get back with you in next couple of business days.

    Regards,

    Manoj

  • 0 in reply to Manoj Santha Mohan
    TI__Guru 55700 points

    Huang,

    PMBus1.3 seems to have lot of new features like AVS Bus, zone read command, IEEE floating point and the 32 bit word etc. While we should be able to get some 1.3 features working on 1.1, we will run into hardware limitation issues pretty soon. Moreover, as of PMBus 1MHz is currently available when PMBus is used in I2C mode. We haven't done any analysis on PMBus support at 1MHz. So, it is safe to say we can't support PMBus 1.3 until we completely understand what features can be implemented using software workaround. As of now, we aren't commissioned to do that analysis.

    Our current objective is to support only PMBus1.2 features.

    Regards,

    Manoj

  • 0 in reply to Manoj Santha Mohan
    TI__Genius 16825 points

    Dear Manoj,

    I understand.

    Wayne