This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCA9546A: VOH levels

Part Number: PCA9546A

Tool/software:

HI Team,

For PCA9546, what is the VOH and VOL level for I2C lines (with VDD=3.3V)?

Thanks and Regards,

Vidhya

  • VOL is specified (as test condition for IOL). VOH is determined not by the AND gate but by the pull-up resistor (if there is any), so the datasheet cannot tell you about it.

  • Hello Vidhya,

    I2C is an open drain protocol, so the mux doesn't output a high voltage signal. Instead it is determined by the PU resistors. 

    As Clemens mentioned, VOL can only be found as the test condition for IOL. 

    Thanks,

    Nir  

  • HI Clemens, Nir,

    VOL =0.4V for IOL 3mA to 7mA

    VOL=0.6V for IOL 6mA to 10mA.

    Our case, IOL is < 3mA. will consider VOL =0.4V

    For VOH, Pull up voltage is 3.3V. will consider VOH=3.3V?

    Please confirm.

    Thanks,

    Vidhya

  • Hey Vidhya,

    The VOH would be around 3.3V here. When your open drain output isn't driving low, you'll simply pull up the line to your Vpu.
    You'll need to size the pullup appropriately though. See I2C Bus Pullup Resistor Calculation

    So for example here at 1mA IOL and 0.4V VOL, with Vpu of 3.3V your minimum pullup would be (3.3-0.4)/0.001 = 2.9kohms. That would be the strongest pullup resistor you can use. If you start going higher, you'll likely struggle pulling the line low in your logic low driving conditions

    Thanks,
    Rami

  • Thanks  Rami