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DM814x Power Sequence.

patrick nefos
Expert 1850 points

Hi,

In review of latest 3.0.8x errata(s), I see that errata 3.0.82 has the "DVDD_DDR (1V5) ramp before 3V3 DVDD supply".

My DVDD rails are 1V8.

This means for me revised turn on order is 1V5 then (3V3 ~ 1V8)* then Core(s).

I assume the 2V delta max 1V8 to 3V3 of datasheet Table 7-6 (2) must still be observed *. To do this on power up, 3V3 must start

slightly before 1V8, but that violates errata 3.0.81. "Ramp the 3.3V DVDD* supplies after the VDDA_1P8 supply is ramped and stable,..."

Can you comment?

Patrick

  • 0
    TI__Guru**** 170625 points

    Patrick,

    Silicon errata is with higher priority than the datasheet.

    BR
    Pavel

  • 0 in reply to Pavel Botev
    Expert 1850 points

    Pavel,

    Does the 2V delta max 1V8 to 3V3 of datasheet Table 7-6 (1) still apply? See Figure 7-2.

    This is on Page 186-187 in the Rev D datasheet DM8148.

    Patrick

  • 0 in reply to patrick nefos
    TI__Guru**** 170625 points

    Patrick,

    The DM814x Silicon errata is the most up-to-date document (15-April-2013), while the last version of the DM814x datasheet/data Manual (revision D) is 14-Sept-2012.

    Per my understanding, now the power-up sequence is:

    1.8V -> DVDD_DDR(1,5V) -> DVDD_3.3V -> CVDD -> CVDD_x

    This Figure 7-2. 3.3 V Supplies Rising Before 1.8 V Supplies Delta, is in case where 3.3V is ramped up before or together with the 1.8V. And this is in discrepancy with DM814x Silicon Errata, Advisory 3.0.81 Power Sequencing: 3.3V DVDD* versus VDDA_1P8

    Details: The Revision D and earlier Data Manuals permit the 3.3V DVDD* and VDDA_1P8 supply to ramp at the same time. This may lead to incorrect I/O bias. The incorrect I/O bias level can cause a reduction in the number of Power-On Hours (POH) for a given device by increasing its failure rate over time. This incorrect I/O bias level will remain until the DVDD_DDR[x] supply is ramped up and stable.

    Workaround: Ramp the 3.3V DVDD* supplies after the VDDA_1P8 supply is ramped and stable, as required by the device-specific Data Manual Revision E and later.
    For the actual "3.3-V DVDD*" power supply names, see the device-specific data manual.

    patrick nefos said:
    Does the 2V delta max 1V8 to 3V3 of datasheet Table 7-6 (1) still apply?

    Based on the above, I think no, if you follow the Silicon Errata guidelines, 2V delta max 1.8V to 3.3V of datasheet does not apply.

    Best regards,
    Pavel