Question about handling various control voltages

[pewt]

I have a circuit involving a quadrature differential encoder and FPGA board. The FPGA board takes 5V logic as input but the supply to the quadrature encoder could be as high as 24V (to offset noise from a VFD nearby). I am already using a line receiver (a TI MC3486N) to combine the differential signals. Is there a chip or simple circuit that can bring down a variety of input voltages automatically?

 

[iop995]

If same GND, a resistor divider on each line, may be a solution.

 

[pewt]

would there be any worries about using a couple resistors (to limit current) and a zener diode? Its a control signal so I'm not really worried about providing current elsewhere in the system.

 

[mikekilroy]

why not just use 5v for encoder vcc like most of us even around vfds? u said u have line drivers, so what is the issue?