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Powering AM335X with DDR3 Support using TPS650250

Raymundo Hernandez-Toscano
Intellectual 810 points
Other Parts Discussed in Thread: TPS650250

I was reviewing the SLVU731A application note on how to power the AM335x family of processors using the TPS650250. It is noted that the part has support for DDR3 when properly configuring the DCDC2 step down converter. However, I still had a few questions regarding the sequencing. Are the LDO's 1.8V rails capable of being run off the DCDC3 3.3V rail and still meet the sequencing requirements for the AM335x with DDR3?

  • 0
    TI__Genius 10885 points

    Possibly, but this would require validation. From what I can tell, the critical factor here is that the 3.3-V IO supplies shall not at any time exceed the 1.8-V supplies by more than 2V.

    According to the AM335x datasheet: "The 3.3-V IO power supplies may be ramped simultaneously with the 1.8-V IO power supplies if the voltage sourced
    by any 3.3-V power supplies does not exceed the voltage sourced by any 1.8-V power supply by more than 2 V.
    Serious reliability issues may occur if the system power supply design allows any 3.3-V IO power supplies to exceed
    any 1.8-V IO power supplies by more than 2 V."


    This is easiest to guarantee when the1.8-V supply ramp up before the 3.3-V supply, and when the 3.3-V supply ramps down before the 1.8-V supply when shutting down.

    However, just to be safe I would recommend checking out the Sitara forum for questions specific to the AM335x, as they may have more details over sequencing limitations for this device:

    e2e.ti.com/.../791