MDIO MDC level translator & buffer [NPI]

Johnny,

This looks interesting.  I'll take a deeper look at it.  I've had additional inquiries on MDIO level shifting at ZTE, but this looks like it is a shifter+fanout. 

Hi, has there been a solution implemented?

If there's no single device which can accomplish it,

then is there a fairly good way to glue this together using existing shifters/translators?

Thanks; Larry.

I see it's been a year since this post started.  Has a solution been implemented?  Were there any multi-device solutions that someone could recommend?

Thanks,

Mike

Hi Mike,

There has been no further development in an MDIO level shifter.  You might want to take a look at the TXB0108 or TXS0108

Hi Johnny,

We're using the txs0108 for a mdio application, but some CFP's are sensitive to rise time.  Can we use the TXB0108 for this application?  I note that MDIO can either be open drain or driven.  The TXB0108 has a note that it is not recommended for OD applications.  And the TXS0108 says to use the TXB0108 for driven applications.  Any comments?  Thanks,

-Jeff

I ended up using a bidirectional translator for MDIO voltage reduction,
  i.e. the the STA operating at 3.3V and the MMD could be anywhere between 1.2V and 3.3V.
But for speed / throughput reasons, never auto sensing.
  If you have it auto-sense to control the direction, I believe that can only run at very, very low clock rates.

So I took the direction control from the STA (as a special output), and used that as the translator's direction control.
  74AVC1T45
  74AVC4T245
  74AVC8T245
The first one there doesn't have an OE input, but you can ground one or both Vcc's to disable both sides.

Doing it this way, although the MMD can operate its output either in open-drain or push-pull mode,
  on the STA side it doesn't know the difference.
At all other times, when STA is driving and translating to the MMD, it will not share the bus with other devices.
To remove that limitation, I would need to use an open drain translator, instead.
  Something that doesn't drive high, or only does on one side of the translator.
  With low valued pull up resistors on the open drain side(s).
Larry

Thanks Larry!  I'm becoming wary of the auto sensing parts.  I've been bitten numerous times by them and the bugs seem to always happen at the end of the project!