I am planning to interface a AC Servo motor driver to an MCU. The MCU generates the clock pulses based on the required speed. For this, the drive supplier has recommended to use a driver like AM26LS31 from TI, as the pulse input stage is configured for dirrential mode. Similarly the drive outputs quadrature signals of the encoder in differential mode and I am supposed to use an AM26LS32 at the recieving end.

Question is what kind of distances these line drivers support ? I will need something like 20m between the servo driver and the MCU in the control panel. As per data sheet, the AM26LS31 will source/sink 20mA. And the switching characteristics are defined with a 30pF loading. Armed with these kind of data how does one arrive at the maximum length of the cable to be used ?

Thanks

Raghu