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TXB0108

Alejandro Gil
Prodigy 50 points
Other Parts Discussed in Thread: TXB0108

I would like to use two TXB0108 in series. I am not sure if this will be a problem to decide the direction of the signals...

The idea is to use one TXB0108 in a board to convert from 5V to 3.3V and on another board attached to the previous one another TXB0108 supplied with 3.3V in both sides. The idea is that the second TXB0108 will be only to protect the FPGA which is connected to it.

Maybe there is a more elegant way to protect the FPGA? Protecting means that if someone plugs something wrong the the TXB0108 will burn and not the FPGA...

  • 0
    TI__Expert 6335 points

    Alejandro,

    I do not think that cascading TXBs will allow for data transmission. This is because the TXB outputs do not have the required drive strength to override the TXB inputs.

    The TXB outputs are only capable of driving high impedance (i.e. low current) loads, while the TXB inputs requires a few mA of drive strength in order to override the hold provided by the weak buffer.

    I can help you select the appropriate product to place in front of your FPGA with a little more information. I am assuming that the FPGA pins are not 5V tolerant, and this why what you are trying to protect. Can you confirm?

    Best Regards,
    Nirav

  • 0 in reply to Nirav Patel
    Prodigy 50 points
    Yes, because they are not 5V tolerant... What can you recommend me?
  • 0 in reply to Alejandro Gil
    TI__Expert 6335 points
    Alejandro,

    I will get back to you on this. Other product lines in TI have ESD protection devices that could protect the FPGA from 5V, but I am not sure if these are for 5.0V transients (i.e. temporary protection) or for prolonged 5.0V (i.e. DC or steady state).

    Best Regards,
    Nirav
  • 0 in reply to Alejandro Gil
    TI__Expert 6335 points

    Alejandro,

    Based on my information, our ESD protection devices support just very short transient events. You could try the ESD/EMI forum for accurate information.

    This may be a question with an obvious answer, but I will ask it anyway:

    Does Board #1 (5V to 3.3V) always connect to Board #2 (FPGA 3.3V)? If so, then could you install the level translator only on Board #2? So that you would have Board #1 (5V) and then Board #2 (5V to 3.3V to FPGA)?

    Best Regards,
    Nirav