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LSF0204: LSF0204 offset, deviation per port

Mason Noh
Expert 2490 points
Part Number: LSF0204

Hi, TI team

I'm testing a level shift for UART from 1.8V to 3.3V.

But A2 has offset voltage (0.5V). Please refer to the below waveform.

Driving current is 8mA.

Could you reveiw my schematic?

And there is deviation per port even same pull up resistor.

example, the voltage on A3 is swing 1.8V~0.49V and A4 is swing 1.8V~0.53V.

  • 0
    Prodigy 50 points
    Hello Mason Noh,
    It looks like that i have the same issue. Did you solve this offset problem?
    Thanks
  • 0 in reply to Tri Duong47
    TI__Guru* 96591 points
    Hi Mason and Tri,
    Yes, it looks like you both have similar issues. Tri, you can see my post on your thread for a more direct answer.

    Mason,
    The 200k resistor in your circuit is not required and should be removed (or replaced with a 0 ohm resistor). There's a video that explains this in detail here: training.ti.com/TLM-LSF-Bias

    Also, the pull-up resistors on the 1.8V side of your circuit are extremely low -- 110 ohm resistors will generate a great deal of current and it's likely that your driver won't be able to pull the line all the way to ground. You can see a detailed video about this topid here: training.ti.com/TLM-LSF-Down

    I would highly recommend watching the whole LSF video series - it's not very long, and covers a lot of information for how the LSF works.