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TXB0104: TXB0104 application

yu peng
Prodigy 10 points
Part Number: TXB0104
Other Parts Discussed in Thread: SN74AHC125, TXB0101

Hello  team

Now,I use TXB0104 for  3.0v  Voltage I2S  transform to 3.3V Voltage I2S,

Can I use it like this  ？  and  how about the data speed,because I only see the input voltage 1.2 ，1.5 ，1.8， 2.5， 3.3 data speed,not 3.0 votage speed？

and  the I2S input data line and out data line need pull uo resistance？

  • 0
    Guru 243220 points

    The TXB also works at all voltages between the voltages listed in the datasheet.

    The TXB must not be used with pull-up resistors.

    3.0 V signals should be read without problems by 3.3 V inputs; see the VIH specification of the receiving device. If you do want to buffer the signals, you can simply use a plain buffer like the SN74AHC125.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Thank you for your reply，But 3.0V do not list in the datasheet，It's right to connect the input with 3.0V I2S and the output with 3.3V I2S?and You mean that the I2S signal of 3.0V can be directly connected to the I2S device of 3.3V. It doesn't need txb0101 chip to convert, right？ If txb0104 is used to turn, the conversion rate of I2S from 3.0V to 3.3V is about？

  • 0
    Prodigy 10 points

    HI  Clemens Ladisch

    In my opinion, the output drive capability of txb0104 is very weak, only 20ua, because I need to connect three I2S devices, two I2S amplifiers and a codec from the output of txb0104. Does this need to add a buffer?

    Do you recommend sn74ahc125. This can do input 3.0V I2S, output 3.3V I2S conversion, and also there is a buffer function

  • 0 in reply to yu peng
    Guru 243220 points

    The TXB might indeed be too weak for multiple devices and/or long traces.

    The datasheet says that at 3 V, the VIH of the SN74AHC125 is 2.1 V. So at 3.3 V, the VIH will be about 2.4 V, which is more than enough for 3 V signals. (I suspect that your I²S devices have similar VIH specifications; you need the SN74AHC125 only if you want buffering.)

  • 0
    Prodigy 10 points

    SN74AHC125 seems to be unidirectional, and I2S signal is bidirectional. If there are other symbol recommended, which can be detected with free direction

  • 0 in reply to yu peng
    Guru 243220 points

    As far as I am aware, I²S is not bidirectional. What are the exact signals you have in your circuit?

  • 0
    Prodigy 10 points

    I'm sorry, it may be my description error. SN74AHC125 can only be A to B, but there is  data in signal in i2s signal, which needs B to A.

  • +1 in reply to yu peng
    TI__Mastermind 23393 points

    Hey Yu,

    It's right to connect the input with 3.0V I2S and the output with 3.3V I2S?and You mean that the I2S signal of 3.0V can be directly connected to the I2S device of 3.3V. It doesn't need txb0101 chip to convert, right？
    Yes, this is what clemens is getting at. If your device that is receiving the signals is a 3.3V device then a 3.0V input would be well above an expected Vih threshold of ~2.4V. Now I can't guarantee that is what your threshold is so checking the device specifications of your I2S device would be recommended. But it should be at around 2.4V. 

    A translator probably won't be necessary here. If you are looking for a buffer though between the inputs the SN74AHC125 device is a good option. For the signal that needs B to A, you can simply wire it opposite of the ones that need A to B. A and B help with identifying directionality but you aren't limited to using all inputs from one device to only the A side. If you use a 3V supply on the AHC your VIH is 2.1V and I would anticipate roughly the same VIH for you A side device and B side device so it should work fine. 
     

     

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Prodigy 10 points

    OK，thank you so much,