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AM1808 power supply ramp

Keigo Ishii
Intellectual 820 points
Other Parts Discussed in Thread: AM1808

Hello.

I found the following topic:

AM1808 Power-on Sequence Timing
http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/108307.aspx

Mr.Paul said that it needs to be ramp up 1.2V to nominal level before starting to ramp up 1.8V.
However, there is no such description in the AM1808 datasheet, there is the ramp up order only in the datasheet.

The following is my understanding. Is it correct?

 - It is necessary to ramp up in the order described in the datasheet.
 - The power supplies need to be stable at nominal level before starting to ramp up next one.

Best regards,
Keigo Ishii

  • 0
    TI__Mastermind 43660 points

    Hello Keigo,

    The AM1808 must be powered on as per the sequence given in the section 6.3.1 of AM1808 datasheet. As per this sequence, the 1.8V has to be powered on only after 1.2V reach the nominal value.

    http://www.ti.com/lit/ds/symlink/am1808.pdf

    Yes, it is necessary to ramp up the power rails (power supplies need to be stable at nominal level before starting to ramp up next one)  in specified sequence. 

    Regards,

    Senthil

  • 0 in reply to Senthilkumar Srinivasan
    Intellectual 820 points

    Hello Senthil,

    Thank you for your quick response.
    Your advise is very helpful for me.
    But, I need also TI's comment.

    To TIer,
    Can you agree with his comment?

    Best regards,
    Keigo Ishii

  • 0 in reply to Keigo Ishii
    TI__Guru** 116100 points

    Hi Keigo Ishii,

    Senthil point was correct.

     - It is necessary to ramp up in the order described in the datasheet.

    Always we have to refer the SoC data sheet for any kind of technical clarifications specific to the particular SoC.

    We have to refer the TRM (technical reference manual) for peripherals detailed explanations.

  • 0 in reply to Titusrathinaraj Stalin
    Intellectual 820 points

    Hello Titus,

    Thank you for your quick response.

    Can you agree also about the following point?


    Yes, it is necessary to ramp up the power rails (power supplies need to be stable at nominal level before starting to ramp up next one)  in specified sequence.

    Best regards,
    Keigo Ishii

  • 0 in reply to Keigo Ishii
    TI__Guru** 116100 points

    Hi Keigo Ishii,

    Keigo said:

     - The power supplies need to be stable at nominal level before starting to ramp up next one.

    Senthil said:

    Yes, it is necessary to ramp up the power rails (power supplies need to be stable at nominal level before starting to ramp up next one)  in specified sequence.

    Yes, Senthil point was absolutely correct.

    Please refer the chapter 6.3.1 in AM1808 data sheet.

    Could you please answer us that Why did you ask this question ?

    Are you facing any problem while you power up the board ?

  • 0 in reply to Titusrathinaraj Stalin
    Intellectual 820 points

    Hello Titus,

    Thank you for your reply.
    I got it.

    > Could you please answer us that Why did you ask this question ?
    > Are you facing any problem while you power up the board ?

    No, the board is working correctly as expected, but 3.3V supply starts to ramp up while ramping up 1.8V supply on the board.
    Therefore, I was worrying about the possibility that other board does not work.
    About how to deal with this, we will decide after careful consideration with our side.

    Senthil and Titus, thank you for your valuable advice.

    Best regards,
    Keigo Ishii