DP83TG720S-Q1: Power off threshold of VDD

Daniel Wang (auto)

Expert 3490 points

Part Number: DP83TG720S-Q1

Hello team,

Happy new year.

Here is a question need your support:

During VDD power-off-> re-power-on, what is the powering off threshold before next powering up?

The VDD power rails include VDDIO, VDDA3P3 and VDD1P0.

Thanks.

over 1 year ago

0 Daniel Wang (auto) over 1 year ago

TI__Expert 3490 points

Add some additional info from another datasheet:

The next power-on cycle is just permitted until all power supplies are below the limit after power-off.

I don’t know whether DP83TG720S-Q1 has specification for that.

0 Melissa Chang over 1 year ago in reply to Daniel Wang (auto)

TI__Genius 14006 points

Hi Daniel,

We usually recommend powering down the device completely to GND. Is the customer unable to do this?

Best regards,

Melissa

0 Daniel Wang (auto) over 1 year ago in reply to Melissa Chang

TI__Expert 3490 points

Thanks for support.

0V is not an actual value. You know, in their real design and test, 0V is impossible due to ground offset, power leakage or noise. Generally, 0.3V maybe a reasonable value.

The problem they are facing is: in some use case, the system need be reset, that causes 720s power-off-> a short while -> power-on again. VDDA3P3 has a long ramp down during power off due to capacitors on power rail discharge.

So, they want to define how long is needed for VDDA3PA ramp down, in which a specified power down threshold value is needed.

0 Melissa Chang over 1 year ago in reply to Daniel Wang (auto)

TI__Genius 14006 points

Hi Daniel,

Yes you are correct, I meant pulling it down to GND, my mistake.

Here are the POR thresholds: VDD : 0.3V, VDDA/IO: 0.5V.

Best regards,

Melissa

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DP83TG720S-Q1: Power off threshold of VDD