DP83825I: Voltage swing(PMD out) with 100Base-TX)

Gerome san

Thank you so much for your reply.

OK, we will check registers 0x30b and 0x30c.
Should we confirm whether Bit cfg_dac_plus_one_val and Bit cfg_dac_minus_one_val are default or not?
And how much is the recommended value?(default??)

And then, we have not received about Rbias voltage yet.
Could you share us it?

Kind regards,

Hirotaka Matsumoto

Hello,

The default values on registers 0x30b and 0x30c are 0x0C00 and 0x0010, respectively. Regarding the RBIAS question, it is more used for fine tuning the voltage. As long as the correct resistor is there (6.49k, 1% tolerance), the register writes should have more significant changes to the voltage level.

Sincerely,

Gerome

Gerome san


Thank you so much for your reply!

Regarding the RBIAS question, it is more used for fine tuning the voltage.
As long as the correct resistor is there (6.49k, 1% tolerance), the register writes should have more significant changes to the voltage level.
->Ok, we understand it. So, we would like to know the how much Rbias pin voltage is.
   And, it will be static DC voltage, right?

The default values on registers 0x30b and 0x30c are 0x0C00 and 0x0010, respectively.
->Just in case, the datasheet shows 7.6.61 DAC_CFG_1 Register (Offset = 0x30C) [reset = 0x20] on the P74.
   "0x0010" is typo, right?


Most of our PHYs are centered around 1V, with ranges spanning between 0.95 and 1.05V.
->We checked the default values on registers 0x30b and 0x30c were 0x0C00 and 0x0020 on the customer's board.
   So, in spite of default setting, the value of PMD output is more than maximum value.
   If you have some advice, could you let us know?


Kind regards,

Hirotaka Matsumoto

Hello,

I will need a little bit of time to gather the answer to the first two questions. I should expect to have answers early next week.

Regarding the value of PMD output, as it is more than the maximum value, I would suggest writing lower values by 1 bit for register 30C (0010 to 0011) and 4 bit increases for register 20B (0C00 to 0C40).

Sincerely,

Gerome

Geroma san

Thank you so much for youre cooperation always.

Regarding the value of PMD output, as it is more than the maximum value, I would suggest writing lower values by 1 bit for register 30C (0010 to 0011) and 4 bit increases for register 20B (0C00 to 0C40).
->We got it. However, in spite of default register, Might PMD output be more than ±1.05V?
   If it is true, we assume that it violates IEEE802.3, right?
   Or, if we set the value within ±1.05V using register, can it regard that it doesn't violate IEEE802.3?
   If you have some knowledge, could you share us?
Kind regards,

Hirotaka Matsumoto

Geroma san

Thank you for your support always!

Our customer checked Rbias pin's voltage.
The result was 1.08mV.(not 1.08V)
It seems that there is abnormal voltage.
We are wait for your reply.

Kind regards,

Hirotaka Matsumoto

Hello,

So long as you are able to get the PHY within the 1.05V level using the register, it does not violate IEEE802.3.

Regarding the RBIAS voltage, this value was not characterized, but we do not recommend changing the RBIAS component value. Changing registers 30b and 30c would be the best way to adjust the voltage level.

Sincerely,

Gerome

Gerome san

Thank you for your reply always!

Regarding the RBIAS voltage, this value was not characterized, but we do not recommend changing the RBIAS component value.
->Ok, we got your comment.
   So, we would like to compare RBIAS voltage whether our customer's board has some trouble or not.
   Could you share us how much the Rbias voltage on the EVM is?
   Of course, we understand this value was not characterized. So we would like to know it as the reference.

Kind regards,

Hirotaka Matsumoto

Hello,

Unfortunately, we do not have this value.

Sincerely,

Gerome

Geroma san

OK, we got your circumstance.
Is it possible to measure it using EVM?
We don't have EVM now.

Kind regards,

Hirotaka Matsumoto

Hello,

Currently it is difficult to get into the lab and record that measurement. However, I can get it to you in a week.

Sincerely,

Gerome

Geroma san

Thank you so much for your cooperation!
We got your situation. It might be affected by COVID-19.
Please take care of yourself.

Kind regards,

Hirotaka Matsumoto

Thank you for your patience.

Sincerely,

Gerome

Geroma san

Thank you so much for your cooperation!!

OK, we got it.

Kind regards,

Hirotaka Matsumoto