Issue understanding pin functions of a programmable current source from manual?
The LT3092 is a floating two-terminal current source.  So you can put it between two nodes in a circuit, and as long as there is enough voltage across it (V(IN) = 1.2V to 40V above V(OUT) in the right direction) it will regulate the current through it to its setpoint.



The Rset pin connects as shown in the diagram.  The 10uA internal current source forces a current in the Rset resistor which develops a reference voltage for the internal error amplifier.  The amplifier will try to force the same voltage across Rout, thus regulating the current to 10uA*Rset/Rout.  So the two terminals of the current source are the "IN" terminal and the junction of Rset and Rout.  You get to choose the two resistors based on your application (read the datasheet section entitled "Selecting RSET and ROUT").