High side switching of a current source with 3.3V logic
When your current setting is very low you will not be able to turn on the P-Channel unless you have a negative rail, which I see you do, so you would need something like this.







simulate this circuit &ndash; Schematic created using CircuitLab

A better solution would be to turn off the current source directly. Perhaps an N-MOSFET tied to the plus pin on your MP38CL.