TXS0104E: MDIO signal voltage level shift

Lacey Lin

Intellectual 2900 points

Part Number: TXS0104E
Other Parts Discussed in Thread: LSF0102

Hi team,

My customer want to find a device that can shift the voltage 3.3V to 1.8V of MDIO signal.

I search the previous posts, you recommend the TXS and LSF part.

But I find the TXS0104 only can support the 2MHz in open drain signal.

The data rate required by customer is about 20MHz.

So can you help to comment if the TXS0104 can support the level shift of 20MHz MDIO signal?

If not, please help to provide the suitable device for the application.

Lacey

Thanks a lot!

over 6 years ago

0 Emrys Maier over 6 years ago

TI__Guru* 97046 points

Hi Lacey,
In my experience, "open-drain" and "20 MHz" don't really go together. Do you have the drive strength and load capacitance specifications of the system?

Is the translation only one direction (3.3V to 1.8V) or is data also being translated up from 1.8V to 3.3V?

0 Lacey Lin over 6 years ago in reply to Emrys Maier

TI__Intellectual 2900 points

Hi Emrys,

I just refer the datasheet, it seems this is related to the driver type: as below

The MDIO signal is bi-direction as the I2C, but the data rate need to support the 20MHz.

Can you help to double check the data frequency of the TXS0104?

Lacey

Thanks a lot!

0 ShreyasRao over 6 years ago in reply to Lacey Lin

TI__Guru 62270 points

Hi Lacey,

TXS010x series cannot support 20Mhz open drain interface data rate.
You will have to consider using the LSF0102 with strong external pull-up resistors (typically 500ohm and assuming 15pF cap load) to enable the 20Mhz signaling. the lower the cap loading, the better.
The IO pin will need external PU on both the sides, but the clock needs only on the output side as I believe that the input is push pull.
Also, note that the driver side must sink all the current generated through the pullup resistors and yet maintain the low level at the output.
Please refer to the LSF training videos here:
training.ti.com/tlm-lsf-basics

0 ShreyasRao over 6 years ago in reply to ShreyasRao

TI__Guru 62270 points

Hi Lacey,

Also wanted to know if you have come across this 20Mhz requirement for MDIO or I2C before or is this is first time?
Is there a special mode which requires such high speed?

0 Lacey Lin over 6 years ago in reply to ShreyasRao

TI__Intellectual 2900 points

Hi Shreyas,
Thanks so much for your reply!
I haven't asked the question before.
And I have checked with my customer, they feedback this is a common data rate of MDIO interface, not special use case.

Lacey
Thanks a lot!

0 ShreyasRao over 6 years ago in reply to Lacey Lin

TI__Guru 62270 points

Thanks for the feedback, Lacey.

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TXS0104E: MDIO signal voltage level shift