DP83867IS 3-supply sequencing, DS vs TS Guide

sergey bartsevich

Other Parts Discussed in Thread: DP83867IR

Hi,

datasheet states that "When operating in 3 supply mode, the 2.5-V VDDA2P5 can come up with or after the 1.8-V VDDA1P8 but not
before it." and troubleshooting guide reads "the VDDA1P8 supply must be stable within 25ms of the VDDA2P5 supply ramping up". If i understand correctly, the later means that 2P5 allowed to ramp up before 1P8 which contradicts to datasheet. Also troubleshooting guide requires foe 1P8 to be shut down before 2P5 on powering down while DS omits powerdown case.

Could you please tell the correct powerup/powerdown sequence and whether it is critical at all in case all 3 supplies ramp up within 15 ms from first to last?

TIA

Sergey

over 9 years ago

0 Rob Rodrigues over 9 years ago

TI__Mastermind 19780 points

Hi Sergey,

In the case that all 3 supplies ramp up within 15ms, you will not have an issue. The datasheet is being revised with the information you see in the TS guide.

The 1P8 supply is recommended to be shutdown before the 2P5 rail as shown in TS guide.

Best Regards,

0 sergey bartsevich over 9 years ago in reply to Rob Rodrigues

Prodigy 130 points

Hi Rob,
thank you for the clarification.
BR,
Sergey

0 Will DeCook over 9 years ago in reply to Rob Rodrigues

Prodigy 240 points

What would be the result of improper power sequencing on the DP83867IR? I have a few prototypes that were designed with the power sequence recommended by the old datasheet (1.8V->2.5V) and haven't yet been able to get reliable operation from the phy. Could the part be damaged from repeatedly applying the wrong sequence for the last 6 months?

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DP83867IS 3-supply sequencing, DS vs TS Guide