Certain hall switch operation

Question

I have a question regarding a Hall sensor IC.

I cant quite understand how is it possible that it can operate only on 2 wires, instead of 3. The way I can think of it is that 2 wires provide Vcc and gnd, and the 3rd one would be the sensind output on the sense resistor (see app note). Now, I know for a fact that it is used in 2 wire config, like Ccc + sensing wire without gnd. It seems confusing. On the schematic there is something like virtual earth inside the IC- does it mean that what hall effect occur when a magnet is close the loop closes inside the IC? I would appreciate an explanation -- but not about how does the Hall effect work, but how this certain IC does.

Answer 1

As shown in the "Functional Description" section of the datasheet, those Hall effect switches use an external sense resistor.

EDIT:

Like so:

^{simulate this circuit – Schematic created using CircuitLab}

And then you measure the voltage across Rsense.