DP83848I: About usage conditions

Hi Rob-san

Thanks for quick reply.
And I'm sorry to be late replying.

Answer of Q1 was desolved.
However I have additional question about Q2's answer.

> For example, using EtherCAT with DP83849 is described in the EtherCAT PHY Requirements guideline.
>There are some notes in there that should be followed, including placing a pull-up or pull-down resistor on XI pins.

Does the above answer refer to what is listed on the following site?

download.beckhoff.com/.../an_phy_selection_guidev2.3.pdf

If it is right,Like EtherCat, do each standared have guidelinesd for each company's PHY?

Best regards,

Gk110

Hello Rob-san

Thanks for your quick reply.

> Unfortunately, other industrial field buses do not give such detailed information about the PHY layer.

If customer is going to use DP83849 for any other industrial field buses,how should they carefully design?

Do you have any information(or document) for design of industrial field buses?

Best regards,

Gk110

Hi Rob,

I'm also working on this with Gk110 and I have one more question about "weak internal pull-down resistor" of PHYADx.

This question is coming from not DP83848 but DP83849I.

could you let me know the value of "internal weak pull-down resistor" since PHYADx connects to external components and it has internal pull-up resistor so they have to care about it.

Thanks,

Regards,

Kai

Hi Rob,

DP83849 internal pull-down resistor will influence external internal pull-up resistor and it will create mid-voltage for less than 10sec.

Question here is if the mid-voltage meets datasheet abso spec (DC input voltage: -0.5 to VCC+0.5), there is no risk to get damage?

BTW, regarding below your comment, I couldn't clearly understand...

" If you have the influence of an external resistor, I'd suggest placing a strong resistor to the value you need. In that case, an external strong pull should not exceed 1.5k".

you commented "placing a strong resistor" but you mentioned "pull(maybe this pull means external pull-up resistor) should not exceed 1.5k".

I'm confusing strong but not exceed...

my understanding for your comment is below figure.

Regards,

Kai

Hello Rob-san

I received one more question about to use for EtherCAT.

In the PHY Selection Guide of BECKOFF, it was written that "X1 must not be floating, add 2.2KΩ pull-down if necessary."
I think that is X1 is connected to CRYSTAL or OSCILLATOR.
Therefore I don't think that the X1 is floating.

Do you know what case does float the X1?

Thanks and best regards,

Gk110