DP83826I: Starp PD/PU setting

Ryuuichi machida

Part Number: DP83826I

Hello,

Let me confirm which information is correct.
According to datasheet (Rev G), you have described as shown below for strap configuration.

However, according to schematic of EVM (https://www.ti.com/jp/lit/ug/snlu262a/snlu262a.pdf), it seems that "2.49k" ohm is used to perform "PD"(Pull Down).
According to above datasheet information, I believe that "1.5k ohm" should be used in this case. However EVM shows oppsition.
Q1. Which one is correct ?

And also, in case of EVM, it seems "ENHANCED mode" is set as default. (This pin is "floating" state.)

So, default value of PHY address is "000". However, you set these pin as "PD" even though it seems state of these pins are internal pull down.
Q2. Why did you add external pull down to these pins ?

Best Regards,

over 1 year ago

0 Alvaro (Al-vuh-roe) Reyes over 1 year ago

TI__Mastermind 19621 points

Hi Ryuuichi,

Q1: Trust the data sheet values. The EVM was made during the early stages of the PHY's development and does not reflect new learnings.

Q2: You are correct, the default state of these pins are all PD, yet there are external PDs on these pins. The internal PD is "weak" and the external PDs are added as a redundancy to guarantee the pin state as low.

Regards,

Alvaro

0 Ryuuichi machida over 1 year ago in reply to Alvaro (Al-vuh-roe) Reyes

Guru 12640 points

Hello Alvaro-san,

For Q1, I understood.

For Q2, Is it recommendation to add external PD ? Or, there is no kind of this description at this time, but do you have plan to add similar notification to datasheet ?

Best Regards,

0 Alvaro (Al-vuh-roe) Reyes over 1 year ago in reply to Ryuuichi machida

TI__Mastermind 19621 points

Hi Ryuuichi,

As a general rule of thumb, if the pin is left floating, there is no need to connect an external strap resistor to confirm its default state. However if that pin is connected to something else, adding an external strap resistor will guarantee we strap the PHY into the correct mode.

Regards,

Alvaro

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DP83826I: Starp PD/PU setting