• TI Thinks Resolved

TXB0108: Input drive strength less than 2mA

Prodigy 110 points

Replies: 3

Views: 46

Part Number: TXB0108

Hi

I have application where I am translating from a 3.3V device (LMK04821) to a 1.8V FPGA. The translation is on the SPI bus but I have noticed the LMK04821 only has a 500uA drive strength on the SDIO pin.

What would be the performance limitation with this drive strength?

If unworkable can you advise on a suitable translator. Maximum clock speed is 20MHz..

thanks

Ken

  • Hi Ken,

    The TXB translator, like all auto-bidirectional translators, requires a driver that can overpower it -- with only 500uA of drive strength, the device could become 'stuck' in one state, not being able to switch.

    I would recommend using the SN74AXC4T774 for 3.3V to 1.8V SPI translation. This device allows for individual direction selection on each channel and avoids all the problems associated with autobidirectional voltage translators. SPI bus typically has 3 signals in one direction and one in the other with no need for changing directions.


    Looking for a low voltage translator? Check out the AXC family that supports 0.7V to 3.3V translation!

    The Logic Minute training page has videos on many interesting topics that all are kept shorter than 5 minutes.

  • In reply to Emrys Maier:

    Hi

    sorry for the slow response, I have subsequently found out that the LMK4821 supports 4-wire SPI so that does make the problem easier. In the end added a buffer onto the MISO line as we are too far advanced with the design to change now however in the future I will consider different translators.

    thanks

    Ken

  • In reply to ken mason:

    Hey Ken,

    Thanks for letting me know. Come back any time!


    Looking for a low voltage translator? Check out the AXC family that supports 0.7V to 3.3V translation!

    The Logic Minute training page has videos on many interesting topics that all are kept shorter than 5 minutes.