DP83822I: Mimimum external pull-up resistor value for RX_ER strap pin

Oba

Part Number: DP83822I

Tool/software:

Hello,

I have a question for a strap configuration.
In my customer case, the RX_ER of DP83822 is connected to AM335x's MII1_RX_ER pin which has an internal pull-down (51~210uA, 3.3V)
They want to set the RX_ER strap to Mode 4. Then they are considering to put an extenral pull-up on the line.
To set it to Mode 4, it may requires 3~4Kohm level pull-up at least. Is it OK to add this leve of pull-up on this line for proper operation?
Or do they need to add a switch to cut the pull-up after the strap timing?

Regards,
Oba

2 months ago

0 Gerome Cacho 2 months ago

TI__Mastermind 34475 points

Hi Oba,

So long as the strap voltage levels per table 8-9 (0.694 x VDDIO) are met with whatever combination, the strap should work accordingly.

Sincerely,

Gerome

0 Oba 1 month ago in reply to Gerome Cacho

TI__Genius 16605 points

Hello Gerome,

Thanks for your reply.
My question is not for the strap configuration itself.
If the RX_ER pin has external pull-up with 3~4Kohm and 100uA pull-down, could it give any bad effect to RX_ER signal in MII operation?

Regards,
Oba

+1 Gerome Cacho 1 month ago in reply to Oba

TI__Mastermind 34475 points

Hello Oba,

What pulldown is there? As the strap pins at worst have 2k on the line (PU pin mode 1), I would assume that the 3-4k PU shouldn't be too big of an issue. It may be best for customer to simulate with IBIS if they are worried about loading the line too much.

Sincerely,

Gerome

0 Oba 1 month ago in reply to Gerome Cacho

TI__Genius 16605 points

Hello Gerome,

Thanks for your support.

Regards,
Oba

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DP83822I: Mimimum external pull-up resistor value for RX_ER strap pin