[dread240]

we're talking the range of .1 ohm to 5 ohm realistically here.

so lets use a 500 ohm digital pot just for reference, and for ease of use it has 50 steps, so 10 ohms resistance per step. We will use a 5 ohm resistor in parallel

500ohm + 5ohm in parallel = 4.9505 ohms

lets go halfway
250 ohm + 5 ohm in parallel = 4.902 ohms (you've already used up 25 steps of the pot and have seen no change

Lets go 98% which would be 10 ohms
10 ohm + 5 ohm in parallel = 3.333 olhms... that's 140ma current from the driver

Our last step should theoretically be no resistance and a straight switch
0 ohm + 5 ohm in parallel = 0 ohms... and that's 620ma current from the driver

It works, technically, but the resolution is crap, hence why you have to use the resistor array and tap different points through a mux (well you could just tap different points themselves and call it a day, but it will use up alot of pins that way, to where as you get 16 positions with only 4 control wires