I am trying to connect two boards together with a few feet of Cat 5e cable. Both boards will be using 3.3v RS-485 transceivers (ISL83483 or similar).
Using this calculator, I entered 3.3v for supply voltage and 100 ohms for Rt1.
It gives a negative number for max. unit loads (-5.85). It says 1.31 if I reduce the noise margin to zero (which isn't good).
I know about the newer failsafe transceivers; however, I want to maintain compatibility with devices using older generation/non-failsafe transceivers. I also know it is commonplace to run short and/or low-speed networks without termination, but I have read multiple good answers on Stack Exchange that conclude termination really should be used.
Am I missing something or is it borderline impossible to have bias and termination resistors using 100 ohm cable and 3.3v transceivers?