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about DVDD3318_X Ramp time for 3.3V in Table 12 of Errata SPRZ303h (TMS320C6748)

Kenji Itoh
Intellectual 420 points

Hi - team,

  My customer have q question rule  for DVDD3318_X Ramp time for 3.3V  in table 12.  So  there is  no rule this ramp time in errata(SPRZ303h)

  http://www.ti.com/lit/er/sprz303h/sprz303h.pdf

  Please teach me this rule ( to xx%  from yy% of  DVDD3318_x).

 Regards,

Kenji Ito

  • 0
    TI__Mastermind 43660 points

    Hello Kenji,

    In reality, there is no ramp up time requirement available for any of the supply rail during power on sequence. However you should be adhere to the power on sequence, the recommendation is to power on the next rail after the first rail reaches its nominal value.

    In order to avoid the issue discussed in errata Advisory 2.3.18, you are required to add certain bulk capacitance to generate the load current of 140mA during the power supply ramp. The table 12 shows the ramp time of DVDD3318 rail for various value of bulk capacitance. This ramp time is solely depends on the capacitance value and there is no requirement on this again.

    Hope you understand.

    Regards,

    Senthil

     

  • 0 in reply to Senthilkumar Srinivasan
    Intellectual 420 points

    Senthil -san

     　Thanks for your reply, I confirm some for ramp time.

    This ramp time(3.3V) is period from F to G in figure 6 on errata Advisory 2.3.18 ?

    In other words、 this ramp time does not contain period from D to E in figure 6.　　So,this period is not charging bulk cap.

    Is this understanding correct?

     regards,

    Kenji Itoh

  • 0 in reply to Kenji Itoh
    TI__Mastermind 43660 points

    Hello Kenji,

    Yes, your understanding is correct. The ramp time for 3.3V is from F to G as in Figure 6 and the ramp time does not include the period from D to E. During D to E, there will be some minor drift up in the undriven DVDD3318_x supplies. This is normal and is not a problem.

    Regards,
    Senthil