• State TI Thinks Resolved
  • Locked Locked
  • Replies 10 replies
  • Answers 1 answer
  • Subscribers 23 subscribers
  • Views 4444 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.

TXB0104 vs TXS0104

Freddy Mendoza
Prodigy 50 points
Other Parts Discussed in Thread: TXB0104, TXB0108

I'm need a level translator to communicate between the MSP430 and my product which has an operating voltage range from about 3 to 5V. I selected the TXB0104 and began reading the datasheet and noticed that in the "Pullup or Pulldown Resistors on I/O Lines" section of the app note it mentioned that this device does not support I2C applications and reffered me to the TXS01XX family. Looking at the TXS01XX datasheet I can't seem to figure out what is the limitation of using the TXB0104 vs the TXS01XX. Could you shed some light on this?

 

Thanks in advance!

Freddy

  • 0
    TI__Expert 6430 points

    Hi Freddy,

    For TXB0104, there is a 4k serial resistor at port. If TXB0104 is used in open-drain application, there is an external pull-up resistor on the port. In general, the pull-up resistor is low than 10kΩ.

    However, if the pull-up resistor is 10kΩ and logic high is transferred, the port voltage will be equal to VCC*Rpull/(Rpull+4k). The voltage on port could be less than Vih and be recognized as low logic.

     If pull-up resistor is more than 10kΩ, the input transition rise rate could be out of required range.

    Thus, TXS01XX is recommended to be used in open-drain application.

    Best Regards

    Lawrence

  • 0 in reply to Wei Lang
    TI__Prodigy 50 points

    Hi Lawrence,

    In most I2C applications I noticed that a pullup resistor is used to set the logic levels of the protocol communication. What are the advantages of using this level translator vs only pullups? 

  • 0 in reply to Freddy Mendoza
    TI__Expert 6430 points

    Hi

    Translator is used to connect two chips which are powered different voltage domain. For I2C application, logic high is achieved by pull-up resistor. But if master and slave are powered at different voltage, pull-up resistor can not solve the communication with different voltage signal. Translator is needed as a birdge between master and slave. In addition, pull-up resistor is integrated in translator. Thus, there is no external pull-up resistor if specific translator is used in the application.

    Thanks

    Lawrence 

  • 0 in reply to Wei Lang
    TI__Mastermind 43875 points

    What is the down side to using a TXS vs TXB in push-pull applications?

    I am trying to reduce my BOM in a design that has both push-pull and open drain.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    TI__Expert 6430 points

    Hi Steve,

    TXB can support higher data rate than TXS device.

    Thanks

    Lawrence

  • 0 in reply to Wei Lang
    TI__Mastermind 43875 points

    Thanks Lawrence.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Intellectual 595 points
    Looking to the respectively product page, it seems to me that TXS is more expensive than TXB device...so I should prefer always the TXB for push pull application.
  • 0 in reply to dtluigi
    TI__Intellectual 2530 points
    Price will depend on other factors including volume. For instance TXB0108 and TXS0108 are similarly priced.
    For choosing between the TXBxxxx and TXSxxxx, we recommend that you decide based on application requirements such as data rates (TXB can do higher), external pull -up resistors (TXS can support) etc.
    Thanks
  • 0 in reply to Jennifer Joseph
    Guru 11785 points
    Hi Sir,
    Sorry, We still confuse at TXB pull up resister.
    We saw you have reply " if the pull-up resistor is 10kΩ and logic high is transferred, the port voltage will be equal to VCC*Rpull/(Rpull+4k)."
    At this formula, our vcc is 1.8v,10k value will larger than 8.2k at value. Right?
    But your next reply is the voltage on port could be less than Vih and be recognized as low logic.
    If our vcc is 1.8v, 10k*1.8/(10k+4k)=1.2857, this value not meet datasheet Vih/Vil.
    Could you help explain it?
    Thanks!
  • 0 in reply to Shu-Cheng LIN
    TI__Expert 6335 points

    Shu-Cheng,

    I think Wei was trying to say that if a strong external pullup/pulldown resistor is used, then the output VOH produced by the TXB0104 may fail to meet the required VIH of an external device. If an external resistor is to be used, make sure it is > 50k.

    As an example:

    Assume that the TXB0104 is connected to a 1.80V CMOS device. Assume that a 10k pullup resistor to 1.80V is connected.

    TXB0104 guarantees a minimum VOH = VCC - 0.4V. For a 1.80V system, this means worst case TXB0104 VOH = 1.40V.

    Due to the 10k pullup resistor, the actual voltage observed by the external device is *not* 1.40V. The observed voltage is actually (1.40)*(10k)/(10k+4.5k) = 0.965V

    The required VIH for a 1.80V CMOS device must be > 0.65*1.80V = 1.17V. Since 0.965V is less than 1.17V, the external device may fail to recognize the TXB0104 VOH.

    FYI - The equations for calculating TXB0104 VOH and VOL are in Section 9.2.2. of the datasheet

    Best Regards,
    Nirav