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Design recommendations for Vcc pins with regulator enabled?

Mathew Maher49
Expert 2115 points

If I've enabled the internal 1.5v regulator (ENZ low), and have no need for external 1v5, what are the recommendations for Vcc pins, i.e. are they best left NC, or should they be decoupled (100nf)?

cheers

Mat

  • 0
    TI__Guru 59540 points

    Hello Mathew,

    I am assuming you are using one of our TMS470MFxxx devices since these are the only ones with an on chip core supply regulator. The Vcc pins must be connected to bypass caps that total a minimum of 1.2uF evenly distributed between the 4 Vcc pins. A recommended implementation is to tie all 4 Vcc pins together and add the recommended caps. Note that these caps are required for regulator stability and as power reserve for regulator responsiveness to instantaneous power demands.

    See the table entitled "Internal Voltage Regulator Specifications" in the datasheet specific to the device you are using for more details and additional requirements for ramp times, ESR, hold times for nPORRST after power up, etc.