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Powering TMS320C6748 - unused modules

Manjula Ellepola
Expert 1335 points

Hi

Can I disconnect unused modules completely from the power rails? That is on my design DDR, USB and SATA is unused. Can the power pins for these sections such as for example USB VDDA18, SATA VDD0 etc be left unconnected? Of the three DVDD3318 A, B and C power domains if only A is used can B and C be left unconnected? Is there a document that covers this?


Thank you in advance.

BR

Manjula

  • 0
    TI__Mastermind 43660 points

    Hello Manjula,

    The easiest way to power these down is via the Power and Sleep Control (PSC) registers. The PSC module allows you to completely disable peripherals. Please refer chapter 8 in device TRM for more details.

    http://www.ti.com/lit/ug/spruh79a/spruh79a.pdf

    If you still want to disconnect the respective power rails, please make sure the unconnected rails should not affect other peripherals. You can find the power group details in the electrical specifications in device data manual and there is no explicit document available.

    Regards,

    Senthil

  • 0 in reply to Senthilkumar Srinivasan
    Expert 1335 points
    Hi Senthil

    Thank you for for the helpful reply. Couple of more questions:
    1. IF the power groups that are not used are left disconnected can this cause latch up problems to other groups that are in use?
    For example if DVDD3318_A is used and group B and C are not used can this cause a problem to group A or any other parts of the system?
    2. Won't the power consumption be less if groups that are not used left disconnected due to less leakage current rather than controlling from the PSC? The leakage of this device is quite high comparatively so it is in our interest to reduce it as much as possible.
    3. Can the USB phy supplies be disconnected if not used? The documentation says that the SATA supplies can be disconnected but does not say the same thing about the USB phy.

    Thank you for your help.

    BR

    Manjula
  • 0 in reply to Manjula Ellepola
    TI__Mastermind 43660 points

    Hello Manjula,

    1. The IO voltages DVDD3318_A, DVDD3318_B and DVDD3318_C are required for proper operation of all the IO pins. If you are not powering any of the group, the respective IO pins powering from that group may not functional. For example, RESETOUT is power from group C and JTAG pins are powered from group B. You could find these details in section 3.8 Terminal Functions of device data manual.

    2. Yes, leaving the unused IO voltage group unconnected may reduce the leakage current. However you have to ensure the IO pins requirement as stated in 1.

    3. Yes, the USB PHY supplies may be left unconnected based on the usage. Please refer the below link where you could find how the unused USB pins can be handled based on the peripheral usage.

    http://processors.wiki.ti.com/index.php/OMAP-L13x_/_C674x_/_AM1x_Schematic_Review_Checklist#USB

    Regards,

    Senthil