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About power-down sequence of C667x

g.f.
Guru 15520 points

Hi,

I have a question about C6678 power down sequence.

I understand that power down sequence is reverse of power up sequence.
But how to control the power down sequence when board's main power goes off before the C6678?
When it's difficult to follow the power down sequence,
as long as all the power rail goes down simultaneously,
may I think that a damage is not given to C6678?

So, we need to follow the power down sequence
when board' main power is active but want to power off the C6678.
Is it correct?

best regards,
g.f.

  • 0
    Intellectual 430 points

    Hello,

    I understand that the power down sequence is the exact reverse of the power-up sequence.(datasheet 7.2.2)

    And I understand  that in a total power down of the system it's difficult to provide any sequencing,but in this case, 

    there is no large amount of static current.

    So When I cut the power of the whole board, There were not any potentiality of  destroying the device.

    Is this my opinion correct ?

    Thanks!


  • 0 in reply to Yi Yin1
    TI__Mastermind 46460 points

    Yi,

    Ideally, the power down sequence is the reverse of the power up sequence with the same maximum durations.  This eliminates excess electrical stress.  Some system designs such as those supporting hot-swap must have gracefull power up and power down sequencing.

    The basic power up sequencing timing from rail to rail is 0 to 100ms.  This means that you could ramp all of the supplies simultaneously as long as CVDD1 does not exceed CVDD and DVDD15 never exceeds DVDD18 per the comments in the tables in section 7.2.1.  Therefore, this also means they can all ramp down simultaneously with the same requirements.

    Also see thread: http://e2e.ti.com/support/dsp/c6000_multi-core_dsps/f/639/t/270308.aspx

    Tom

     

  • 0 in reply to Tom Johnson 16214
    Guru 15520 points

    Hi Tom,

    Thank you for the response.

    I understand that all power supply can be ramp down simultaneously
    as long as CVDD1 does not exceed CVDD and DVDD15 never exceeds DVDD18.
    Let me check one more thing.

    Is there any requirement between CVDD and DVDD when ramping down simultaneously?

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Mastermind 46460 points

    g.f.,

    None other than ramping down simultaneously.  The 2 critical ones were already highlighted.  You cannot have a single rail powered while the others are powering down.

    Tom

     

  • 0 in reply to Tom Johnson 16214
    Guru 15520 points

    Hi Tom,

    Thank you for the reply.
    Ok, I understand.

    best regards,
    g.f.