DP83867IS: Power on Sequence

Atsushi Takahashi

Part Number: DP83867IS
Other Parts Discussed in Thread: DP83867IR

Hi Team,

This question about DP83867IS and DP83867IR.

The customer is using it in Three-supply mode(1.1V, 1.8V, 2.5V).
They understand that the correct power on sequence should be to ramp up VDDA2P5(2.5V) then VDDA1P8(1.8V).
However, VDDA1P8(1.8V) ramps up before VDDA2P5(2.5V) due to mistake design on their board.

When VDDA2P5(2.5V) starts to rise after VDDA1P8(1.8V) rising, VDDA2P5(2.5V) will be clamped at 1.5V on the way.
We would like to confirm whether this behavior is normal or not.
That is, does this device have a clamp circuit for protection, and if VDDA1P8(1.8V) rises first, VDDA2P5(2.5V) will be clamped at 1.5V?

Please check the attachment for actual power on sequence.

Best Regards,

6320.DP83867ISRGZ_DP83867IRPAP_Power up sequence.pdf

over 1 year ago

0 Evan Mayhew over 1 year ago

TI__Mastermind 24998 points

Hi Takahashi-san,

Thanks for your query. The clamping is expected in this case - does the customer see any issues with functional tests?

Is it possible for customer to add delays to ramp up to meet sequencing requirements?

Best regards,

Evan

0 Atsushi Takahashi over 1 year ago in reply to Evan Mayhew

Expert 1415 points

Hi Evan-san,

Thank you for your reply.

There are no known issues at this time.
The customer would like to use the device with this design without fix unless it causes damage or malfunction.
Do you have any advice in this regard?

0 Evan Mayhew over 1 year ago in reply to Atsushi Takahashi

TI__Mastermind 24998 points

Hi Takahashi-san,

I've confirmed with team - there is no concern of damage to the PHY for this case. The internal clamping / back power will account for this margin in sequencing.

Thank you,

Evan

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DP83867IS: Power on Sequence