DP83867IR: Limitation of Power-on Timing

Hello G.f, 

Thank you for the query.

Can you confirm the timing is in ms and not ns ?

Regards,

Sreenivasa

Hi Sreenivasa,

Thank you for the reply.

It was just an example, so there is no specific value right now.
We just would like to know if there are any restrictions.

best regards,
g.f.

Hello G.F, 

Noted. Please ensure the all the supply ramp is > 500us and follow the datasheet timing.

If you do not have additional questions, please close the thread by pressing the resolved button.

Regards,

Sreenivasa

Hi Sreenivasa,

Thank you for the reply.

I couldn't find any timing for two power supply mode in datasheet.
Do you mean that there are limitation to the time from 1.0V startup to 2.5V startup completion?
And do you mean that all power supply's ramp time need more than 500us?
Could you please take a look at the attached file?

DP83867IR Power Timing.pptx

best regards,
g.f.

Hello G.f, 

Thank you for the diagram. 

There is no requirement for the sequence of the supplies when operating in two-supply mode. 

The diagram you have shown for All power ramp time is correct, Please follow the same. All power supply ramps should be 500us or more.

What is the ramp time you are seeing or expecting in the system.

Regards,

Sreenivasa

Hi Sreenivasa,

Thank you for the reply.
I'm so sorry, but I'm not clear about the timing of power-on yet.

There are no expected ramp time in system yet.
The customer are just researching the timing specification of DP83867 to design their product right now.
<Question 1>
By the way, I understood that the each power supply ramp up(from the start supplying to stabilize) minimum time is 500us,
but what is the maximum time? In the DP83867IR datasheet, there are no information about the power supply ramp time. Will it be updated in the near future?

<Question 2>
I already know that there is no required sequence for the two-supply mode as it's written in the datasheet.
My customer are thinking of starting to supply 1.0V first and then supplying 2.5V.
What they want to know is, if there is timing limitation within from the beginning of 1.0V ramp up to 2.5V stable or not?
In three-supply mode, there is a limitation that VDDA1P8 must be stabilized within 0ms to 25ms from the start of VDDA2P5 ramp up.
So, are there similar limitation in two-supply mode,
such like 2.5V must be stabilized within XXXX[ms] to YYYY[ms] from the start of 1.0V ramp up?

best regards,
g.f.

Hello G.f, 

Thank you for the mail.

Question 1 

The recommended max ramp time recommended would be around 120ms. We would include this in the datasheet in the future update.

Question 2

For the 2 supply configuration there is no supply sequencing specified or recommended.

Regards,

Sreenivasa

Hi Sreenivasa,

Thank you for the reply.

Kallikuppa Sreenivasa said:

Question 1 

The recommended max ramp time recommended would be around 120ms. We would include this in the datasheet in the future update.

Is this recommendation only for two-supply mode? If this recommendation also for three-supply mode, I think that the max ramp time 120ms won't meet the  requirement of "Table 134. Three-Supply Mode Power Supply Sequence" (the beginning of VDDA2P5 ramp up to VDDA1P8 stable), because its max is 25ms.

Kallikuppa Sreenivasa said:

Question 2

For the 2 supply configuration there is no supply sequencing specified or recommended.

Thank you for the answer. I understood as that there are no limitation of the time between starting of 1.0V ramp up to 2.5 stable also.