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TMS320C6748: TMS320C6748 Errata (SPRZ303H): 2.3.18 DVDD18 Can Pull Up to 2.7V When Using Dual-Voltage IOs at 3.3V

Adrian Helwig
Expert 3810 points
Part Number: TMS320C6748
Other Parts Discussed in Thread: LP2953

Hello Team,

my customer is planning to use our C6748 and we are now discussing power supply for that DSP.

He asked about the following Errata:

www.ti.com/.../sprz303h.pdf

and especially about the point 2.3.18

The customer is planning only with 30mA for 1.8V supply (I attached Block diagram)

Could You please provide power supply proposal to satisfy this requirement

best regards

AdrianGEM2 Power v3_TI_proposal.pdf

  • 0
    TI__Guru**** 161600 points
    Hi,

    We're looking into this. Feedback will be posted directly here.

    Best Regards,
    Yordan
  • 0
    TI__Mastermind 42545 points
    Hi Adrian,
    You pointed to section 2.3.18 in the errata which clearly defines a problem that could be present with the power supply topology that you have attached. That section also has detailed workarounds for the issue described. If the customer's design is not power sensitive a combination of bulk caps and a load provided by a pull down resistor could be used to ensure that the 1.8V supply output remains stable. If the customer has a design that is more power sensitive, a power supply that provides active output discharge and overvoltage protection would be a better choice. A quick search pointed me towards the LP2953 which has an enable, a power good output and has active output discharge. I suggest you contact the power supply team for more details on whether this is the best solution.
    Regards, Bill
  • 0 in reply to Bill Taboada
    TI__Expert 4860 points
    Hi Bill,

    My customer is facing same problem and already shipped some units of his products out to end customer.
    My question is that this problem could damage C6748 if DVDD18 pull up to 2.7V, is this correct please?

    Regards,
    Luke
  • 0 in reply to Luke Chen
    TI__Mastermind 42545 points
    Hi Luke,
    Let me get some clarification. Are you saying that the customer design uses a power supply that does not meet the errata recommendations or are you saying that the customer has observed the 1.8V power supply being pulled to 2.7V?
    Regards, Bill
  • 0 in reply to Bill Taboada
    TI__Expert 4860 points
    Hi Bill,

    Yes, and this customer already shipped some units to his end customer before recognizing this problem.
    We say DVDD1.8 should not exceed 2.0V in the absolute maximum rating table and he wants to make sure whether or not this problem will damage C6748 if the 1.8V power supply being pulled to 2.7V.
    Please advise your idea, thanks for help.

    Regards,
    Luke
  • 0 in reply to Luke Chen
    TI__Mastermind 42545 points
    Hi Luke,
    If the customer has units in the field with this problem, the C6748 component may be damaged. There isn't anything that can be done with software to prevent this problem from occurring. I don't have any work around for existing boards that did not follow the errata.
    Regards, Bill