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PCA9306 line exceeds the 400pF I2C spec

Other Parts Discussed in Thread: PCA9306

Hello,

I'm looking to use the PCA9306 on a board that will be connected to the I2C master on the VREF2 side through a 4.5 m cable.  I’m not sure of the exact capacitance of the cable yet but if it exceeds the 400 pF I2C spec, what kind of behavior will the PCA9306 exhibit?  It doesn’t seem to have any one-shot accelerators in the chip, from which I’ve seen oscillations with high output capacitances.  Would I just see a slower edge and be unable to run the I2C signal at a high rate?  We are running our I2C at 100 kHz.

 

Thanks,

-Michael

  • Hi Michael,

    If you were to exceed the 400pF I2C spec, there will be issues in the speed of the rise time to hit 70% of VCC. A workaround to this would be to increase the pull-up strength on your I2C bus. However, this may cause your current spec to be out of spec for your slave device. Another issue that could occur, is that your VOL could be increased since this device is merely an I2C switch. VOL = VIN + Voffset.

    Thanks,
    Siby