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Original question:

TXS0102: Reg :- VOH specification of the TXS0102 device

TXS0102: Reg :- VOH specification of the TXS0102 device

Kalaiyarasi Mani
Prodigy 150 points
Part Number: TXS0102
Other Parts Discussed in Thread: DP83867IS, LSF0102

Hi,

I have one more query related to using TXS0102 device on MDIO interface with TI DP83867IS ethernet phy.

As per the TXS0102 datasheet it supports 24 Mbps (Push Pull) / 2 Mbps (Open Drain).

 

From the TI DP83867IS datasheet, it is not specified if the MDIO IO buffer is open drain.

TI DP83867IS datasheet, SNLS504C –OCTOBER 2015–REVISED DECEMBER 2019, pg27, section 8.4.2 specifies that  “The MDIO pin requires a pullup resistor (2.2 kΩ) which, during IDLE and turnaround, pulls MDIO high.”

From this it is not clear if the MDIO signal is Push Pull type or Open Drain?

  • Please advise if you have that information.

 

The RFSOC device driving the MDIO interface supports data rate of 2.5Mbps. My understanding is that it IOs are push pull type. So if the TI DP83867IS ethernet phy MDIO pin is Open drain type, then we may have to evaluate other level translator options to support 2.5Mbps.

  • Please let us know your inputs on this?

 Regards,

Kalaiyarasi M

  • Guru 317370 points

    The DP83867IS's MDIO output, when active, is push/pull. The pull-up resistor is needed only when none of the devices on the bus is transmitting.

  • Guru 317370 points

    Actually, the DP83867IS's MDIO output is open drain. So it will not be able to drive the TXS at 2.5 Mbps.

    The LSF0102 is a device that is able to translate at higher speeds. However, high speeds require very strong pull-up resistors, which increase the actual VOL of the DP83867IS and the controller. (And the achievabke speed depends on the total capcitance of the LSF and the traces, so the only practical way to size the pull-up resistors is to experiment with an oscilloscope.)