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TXS0108E

srimannarayana masimukku
Prodigy 40 points
Other Parts Discussed in Thread: TXS0108E

Hi,

I want to use TXS0108E for my applications. in my application i want to convert the voltage levels from 5V or 3.3V to 1.8V or 2.5V. For the I2C , SPI and UART should I use the TXS0108E .can any body please suggest me for right selection.

  • 0
    TI__Mastermind 30280 points

    Hello,

    Based on the voltage levels you have stated, the TXS0108E would work if the 1.8V/2.5V side is wired to Port A and the 3.3V/5V side is wired to port B (VCCA<=VCCB) The TXS0108E is designed to work for both Open-Drain (I2C) and Push-Pull (SPI) interfaces.

    The one thing I am not sure about is why you are saying 1.8V or 2.5V and 3.3V or 5V.

    Are you trying to use this translator to simultaneously transmit ALL 3 types of communication simultaneously from system A to system B? (i.e. bits 1 & 2 --> SCL & SDA, pins, bits 3-6 --> SPI, and bits 7 & 8 --> TxD & RxD)

    Or would you be interested in a discrete solution for I2C, SPI, and UART using 3 different translators?

    Maybe you could draw a block diagram of side A and side B of your system to give me a better idea of your meaning.

    Regards,

    Brian

  • 0 in reply to Brian Berner
    Prodigy 40 points

    Hai Brian,

     

    Thank for the repply.

    Actually  we have two types of FPGA boards. one board is 1.8V IO compatible and another board is 2.5V IO compatible. thats why i mentioned 1.8/2.5v.we want to prepare the level shifter board for two FPGA boards.for the other side B the IC's which we want to use are some have 3.3v IO levels and some have 5V IO levels with I2C,SPI andUART interfaces.

    Can you please suggest me which one is correct ,to use single chip for    all the interface(i.e. bits 1 & 2 --> SCL & SDA, pins, bits 3-6 --> SPI, and bits 7 & 8 --> TxD & RxD) or better to use individual chips for each interface.

     

     

  • 0 in reply to srimannarayana masimukku
    TI__Mastermind 30280 points

    As far as I can tell, as long as each of the Port A inputs are individually compliant with the VIL and VIH recommendations given the VCCA voltage you choose (1.8V or 2.5V), and as long as each of the Port B inputs are individually compliant with the VIL and VIH recommendations given the VCCB voltage you choose (3.3V or 5V) according to the different specs for push-pull and open-drain in the datasheet, then the pins operate independently and you can use this 1 part to satisfy your system.

    Please read the datasheet carefully to understand what I mean, and in the meantime I will get in touch with an expert who can verify this claim.

    Regards,

    Brian

  • 0 in reply to Brian Berner
    Prodigy 70 points

    Hi Brian

    i am using the same kind of setup. the TXS chip has to level traslate 3.3V <-> 5V for both push-pull and open drain IO's. But i am facing issues with this chip while translating push-pull IO's , the output starts to oscillate. For open drain IO's it is working fine. I have not used any pull ups on the lines.

    we have 7 seven such lines , 2 were working fine for both the IO's , remainig 5 only works for open drain IO's. Do you have any suggestions to resolve the issue. Will the TXS are designed to drive high capacitive loads ( >70pF)? the drive strength should be >2mA to drive the TXS chip also?.