DP83822I: Timing of Hardware Reset de-assertion

Hi g.f.

The RESET_N pin does not need to wait for supplies to become stable. An internal reset is generated when the VDDIO/AVDD supplies are ramped up.

The POR time is typically 200ms and follows the timing shown in the Power-Up Timing time T2 when measured from supply ramp up and RESET is pulled high.

Best Regards,

Hi Rob,

Thank you for the reply and I understood that there are no timing specification between VDDIO/AVDD and RESET_IN.
But sorry, I have a few additional question about DP83822I reset.

>"An internal reset is generated when the VDDIO/AVDD supplies are ramped up."
Q1.
Do you mean that internal reset be generated even if RESET_N kept asserted after power are ramped up?
Or does RESET_N also need to be deasserted for internal reset be generated?


Q2.
Does RESET_N and internal reset(POR) will force same reset process?

Q3.
What is the use case of RESET_N?
Is it optional and can be always tied to High(deassert) if hard reset for DP83822 are not required
during normal operation?

Q4.If I don't use RESET_N, can it be left floating because it has internal Pullup?

Q5.
The description of RESET_N in DP83822i datasheet page.5 Pin Function table,
it said as follow:
*****************************************************************************
Asserting this pin low for at least 1μs will force a reset process to occur.
*****************************************************************************
But Reset Timing table in page.11, it said RESET pulse width is 10μs(Min).
Which is true? Is it 1μs?

best regards,
g.f.

Hi g.f.

Q1. Yes, even if RESET_N is kept asserted after power up, the internal POR still occurs.

Q2. Yes, they force the same process.

Q3. RESET_N can be used if any error occurs with the device during normal operation. Sometimes it is used by customers to restart auto-negotiation when a link is not present.

Q4. It can be left floating.

Q5. I have to look into this.

Best Regards,

Hi Rob,

Thank you for answering to my questions.
I understood about Q1-Q4.

About Q5, in other TI EtherPhy Product (ex. TLK105L, DP83848, DP83867),
the RESET pulse width is 1μs(Min), so I'm guessing DP83822 RESET pulse width is also 1μs(min) .
But I will wait for the answer from you.

best regards,
g.f.

Hi Rob,

Thank you for the reply.
I understood.

best regards,
g.f.