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ADC12DL3200: Power Sequence

IT
Prodigy 70 points

Part Number: ADC12DL3200

Hello E2E,

I have some questions about the power sequence of ADC12DL3200 on page 131 in datasheet.

The power sequencing requirement is VA19 ≥ Vx11.

What is the impact if we don't follow the rule?

May it damage the device?

The PG outputs and EN inputs of the regulators can be used to achieve the power-up sequencing requirement.

Can it also be achieved during power-down?

Supply Current :  IVA19 = 1300mA   >   IVA11 = 700mA  

The VA19 voltage may drop faster than VA11 during power-down.

Does VA11 need additional protection?

Sincerely,

IT Hung

  • 0
    TI__Guru* 91947 points

    IT,

    If the rule of VA19 ≥ Vx11 is not followed the device could get damaged. This should be avoided. Doing this can damage the part but the damage is less likely if the duration is short. There is no guaranteed though that short violations of this rule won’t damage it or won’t let the device age faster.

    Same goes for the power down sequence.

    Regards,

    Jim

     

  • 0
    Prodigy 70 points

    Hi Jim,

    In the EVM board (ADC12DL3200EVM),

    It follows the example on page 130 in datasheet (ADC12DL3200) to achieve the power-up sequencing requirement.

    Does this application have problems during power-down?

    The VA19 voltage may drop faster than VA11 during power-down.

    Sincerely,

    IT Hung

  • 0
    Prodigy 70 points

    Hi Jim,

    In the EVM board (ADC12DL3200EVM),

    It follows the example on page 130 in datasheet (ADC12DL3200) to achieve the power-up sequencing requirement.

    Does this application have problems during power-down?

    The VA19 voltage may drop faster than VA11 during power-down.

    Sincerely,

    IT Hung

  • 0 in reply to IT
    TI__Guru* 91947 points

    IT,

    I did not design the EVM but it should have been so that the power down sequence is done properly.

    Regards,

    Jim

  • 0
    Prodigy 70 points

    Hi Jim,

    In our power design, the power source will be divided into Analog Power and Digital Power.

    VA19 and VA11 are provided by Analog Power.

    VD11 and VLVDS are provided by Digital Power as shown below.

    The power design is also based on EVM so that the PG and EN pins of the regulators can be used to achieve the power-up sequencing requirement.

    However, the supply current IVA11 and IVD11 are both less than IVA19, so the VA19 voltage may drop faster than Vx11 during power-down.

    We are worried that this design cannot meet the power-down sequencing requirement carefully.

    It will cause the device to get damaged.

    Can TI provide some suggestions to avoid this situation?

    Sincerely,

    IT Hung

  • 0 in reply to IT
    TI__Guru* 91947 points

    IT,

    I would suggest adding larger bulk caps on the VA19 which would take longer to bleed off when power is removed. I would also suggest contacting the power group forum if you are using TI LDO's. They may have other suggestions.  A power sequencer would be another good option as these have programmable enables.

    Regards,

    Jim