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TXB0108 Oscillation

user1418213
Prodigy 20 points

Other Parts Discussed in Thread: TXB0108

Hi,

I´m buffering an Arduino Due´s digital pins with  TXB0108s, in out direction (Due (3.3V) to world (5V)), the output voltage is ok when unloaded, but if I tie a 470R resistor to it, it begins to oscillate at 40MHz. The TXB0108 is bypassed with a 100nF ceramic cap.

Any ideas?

Frank S. Mueller

  • 0
    TI__Mastermind 24896 points
    Hello Frank,
    Can you show me a schematic and waveforms? What do you mean tie a 470 Ohm resistor to it? In series with signal? from port to ground? Are you using a cable? How long is it? Do you have information about the cable?
    -Francis Houde
  • 0 in reply to fhoude
    Prodigy 20 points

    Hello Francis,

    Thanks for the prompt reaction. I tied the 470Ohm R to ground, no cable, PCB. The schematic is fairly simple by now, Arduino Due, TXB0108, 470 Ohm, nothing else.

    The first plan is to drive a low current Optocoupler Cam trigger with the TXB0108, but we tried to be flexible.

    I can´t get the waveforms out of the scope, but looks like a low passed 25MHz square, an oscillator as in teh textbook.

    Greetings

    Frank S. Mueller

  • 0 in reply to user1418213
    TI__Mastermind 24896 points
    Hello Frank,
    Are you trying to drive an opt coupler? The TXB0108 is not designed to drive large loads. 750 Ohms is to large a load. We have other devices that have much higher drive capabilities. Can you tell me the opto-coupler you are using and what all 8 lines are being used for? Do you need bidirectional capabilities? I can help you select the correct level shifter/translator for you application if you tell me more about what you are doing.
    -Francis Houde