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TMS320F28388D: power sequence for 28388

Sammi Shang
Expert 4450 points
Part Number: TMS320F28388D
Other Parts Discussed in Thread: TPS62420,

Dear team,

Customer want to know any power sequence requirement for TMS320F28388? When use TPS62420, the schematic add a diode between 3.3V output and 1.2V output. Do you know the reason?

Thanks.

Best regards,

Sammi

  • 0
    TI__Genius 15385 points

    Hi Sammi,

    Is your question, why does TPS62420 have a diode connection on 3.3V and 1.2V?

    Please refer TMS320F28388D Datasheet  section 5.8.1 on Power Sequencing requirement.

    Regards,

    Nirav

  • 0 in reply to Nirav Ginwala
    TI__Expert 4450 points

    Hi Nirav,

    Thanks for your response. Customer want to know:

    1. If they could use 2 LDO for VDDIO/VDDA and VDD power supply?

    2. 5.8.1 suggested add a 56ohm between VDD and VSS, but I did not see on schematic.

    3. Seems no special sequence for 3.3v and 1.2v power supply?

    4. Why add the diode D4 between 3.3v output and 1.2V output?

    Thanks.

    Best regards,

    Sammi

  • 0 in reply to Nirav Ginwala
    TI__Expert 4450 points

    Hi Nirav,

    Would you kindly help give some suggestion of below questions?

    Thanks.

    1. If they could use 2 LDO for VDDIO/VDDA and VDD power supply?

    2. 5.8.1 suggested add a 56ohm between VDD and VSS, but I did not see on schematic.

    3. Seems no special sequence for 3.3v and 1.2v power supply?

    4. Why add the diode D4 between 3.3v output and 1.2V output?

    Best regards,

    Sammi

  • 0 in reply to Sammi Shang
    TI__Genius 15385 points

    Hi Sammi,

    Here are answers to your questions:

    1. Yes that should be fine.

    2. Currently we do not have schematic, but implementing 56ohm resistance between VDD and VSS should be fairly straight forward.

    3. If you look at the Power Sequencing requirements in the data sheet, you will see it states "During the supply ramp, VDD should be kept no more than 0.3V above VDDIO".

    4.  D4 is a schottkey diode, using a Schottky diode from OUT to IN will keep the body diode in the LDO from conducting when the output voltage exceeds the input voltage. You must use Schottky diodes because of their low forward voltage. Traditional diodes have a much higher forward voltage than Schottky diodes

    Regards,

    Nirav