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TMS320F28P650DK: internal VREG supply

Aleksandr Sheianov
Prodigy 185 points

Part Number: TMS320F28P650DK
Other Parts Discussed in Thread: TMDSCNCD28P65X, LAUNCHXL-F28P65X,

Tool/software:

Hi,


I have a question about VREG functionality. In the datasheet of TMS320F28P650DK it can be found that the internal regulator 1.2V VREG is availiable. In addition according to the power consumption graphs it seems that using the internal regulator is more efficient as it consumes less power compared to the external power supply. However, I noticed that in both reference designs for this microcontroller (TMDSCNCD28P65X and LAUNCHXL-F28P65X) the external 1.2V voltage supply is used. Therefore, I would like to ask what are the benefits of using the external 1.2V power supply? What kind of special care should be taken if I want to use the internal power supply ( the advantage of the reduced BOM count seems to be intresting) ?


Thank you very much for your feedback.

  • 0
    TI__Guru* 85070 points

    The efficiency difference will be dependent on the external supply source if you bring the 1.2V externally. The reasons that the power consumption graph for internal supply are lower than external supply is that even when the VDDIO is at its max, the internal regulator keeps the 1.2V at that nom voltage.  When we measure for external supply for the core, we are apply the max voltage on it as well. This is why it appears that the internal regulator is "better".

    The reason to use off chip supply is if instead of an LDO you had a switching regulator, which would be more efficient than our on chip VREG, which is an LDO.

    There are also use cases that require monitoring of the core supply, but due to the nature of how this is implemented, a supervisor cannot be used on the internal regulator output; so if that is a requirement 1.2V would need to come from an external source.

    Best,

    Matthew