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TXB0108: I/O Drive strength

Miteshkumar Dalabhai Patel
Intellectual 2410 points
Part Number: TXB0108

Hi....

Section 8.3.2 in TXB0108 datasheet mentioned about I/O drive strength of driver to TXB0108  should be +/-2mA.

Which device satisfy this condition as to get 2mA drive strength source should need swing of 8V approx. if TXB0108 is biased at 1.8V?

According to equation, Vt = Vcci/2 = 1.8V/2 = 0.9V. If we approximate this number to Vt = 1V, value come out will be 1V/4K = 0.25mA

Kindly clarify why 2mA source is needed? and if needed how equation is justifying this condition?

My customer wants to use this device for 1.8V to 3.3V conversion.

Mitesh

  • 0
    TI__Guru 61870 points
    Mithesh,

    The 2mA is given as a safe value to ensure the reliable switching of the IO ports and includes all the tolerances of the internal resistor, process/ temp variations. Of course, the 2mA is assuming the worst case condition of 5V operation and would include 10% margin on voltage error as well.

    Assuming 2mA for the 5V case, it will scale down to 1.8 as follows:
    1.8*2mA/5V = 0.72mA.
    For 3.3V, it would be 1.32mA.

    So, for ensuring proper operation, I would suggest having atleast 1.5mA drive strength.

    Please let me know if anything else.