Pullup-pulldown resistors over A and B pins

Hello,

 The receiver has a threshold voltage which determines if the output is 1 or 0.   This threshold value may be any value between -200mV and +200mV and can vary between parts as well as drifting over time or temperature.  Thus when VA-VB is between -200mV and +200mV, the receiver's output of the MAX22028 is undetermined.  It may be 1 or it may be 0.   To prevent this the biasing network of the pull-up, pull-down and bus terminating resistors is used to assure that the idle state of VA-VB is > +200mV and remains 1.

  Its possible, that with your idle value of 70mV, the receiver is correctly recognizing the idle state and this would mean that the receiver's threshold is below 70mV.  Since this could change for various reasons, a more robust design would set the idle voltage to be >200mV.

Eric

Hello,

 The receiver has a threshold voltage which determines if the output is 1 or 0.   This threshold value may be any value between -200mV and +200mV and can vary between parts as well as drifting over time or temperature.  Thus when VA-VB is between -200mV and +200mV, the receiver's output of the MAX22028 is undetermined.  It may be 1 or it may be 0.   To prevent this the biasing network of the pull-up, pull-down and bus terminating resistors is used to assure that the idle state of VA-VB is > +200mV and remains 1.

  Its possible, that with your idle value of 70mV, the receiver is correctly recognizing the idle state and this would mean that the receiver's threshold is below 70mV.  Since this could change for various reasons, a more robust design would set the idle voltage to be >200mV.

Eric

Thank you so much this is exactly was i expecting: i'll change the pull-up/down resistors to 1K so the Va-Vb in idle state will be about 250mV to be into the range of '1' in the idle state.

sounds good!