• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 18 subscribers
  • Views 250 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TXB0108: Input drive strength less than 2mA

ken mason
Prodigy 150 points
Part Number: TXB0108
Other Parts Discussed in Thread: LMK04821, SN74AXC4T774

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

  • 0
    TI__Guru* 96591 points

    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.

  • 0 in reply to Emrys Maier
    Prodigy 150 points

    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

  • 0 in reply to ken mason
    TI__Guru* 96591 points

    Hey Ken,

    Thanks for letting me know. Come back any time!