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Warning - Using UCD9244 for C6678 Power Rails

Richard Marsh
Intellectual 760 points
Other Parts Discussed in Thread: UCD9244, UCD9222, UCD9224

Hi All,

I have just come unstuck.  I was going to use a UCD9244 for the four C6678 rails (CVDD, 1V0, 1V5, 1V8).  

However, despite the UCD9244 datasheet saying "Supports Voltage Margining & Sequencing", I have been informed that it's sequencing options are very limited.  It can only sequence automatically using a time delay i.e.  it cannot delay power up of Rail #2 until Rail #1 is stable.  Also, as I understand it, it won't monitor Rail #1 and prevent Rail #2 from powering up if Rail #1 fails.

My reading of the C6678 power sequencing is that we need to monitor the rails in the sequence and that a time delayed power up sequence isn't good enough.

It looks to me like the UCD9244 is only good for the Smart Reflex CVDD when you have four C6678 DSP's on the board, and that you can't use it for any of the other rails.

Richard

  • 0
    TI__Genius 13700 points

    The UCD9244 has typically been used in systems where multiple DSP processors requiring the Smart Reflex interface are implemented, although it has been used by some customers for other rails in their DSP power system but this requires the use of an additional sequencer/health monitor (ex. UCD90xxx).

    Most single/dual C667x implementations have used the UCD9222 (which has two individual enable inputs, ENx, and two individual power good output, PGx) with an additional UCD9224/46/48 digital controller which can handle the additional timing requirements of the C667x specification to implement their remaining system voltage requirements.

    The more advanced sequencing capabilities of the UCD9224/46/48 had to be removed from the UCD9222/44 to incorporate the VID capabilities.