In "Brothers," after Data has commandeered the bridge, Captain Picard wonders if the computer would supply them with the exact stun setting required to incapacitate Data.
It seems unlikely to me that even maximum stun would affect Data. Admiral Quinn, while enhanced by the symbiont, was only knocked out with a phaser set to kill.
In-universe, perhaps Picard was ignorant of Data's durability, or maybe he wasn't fond of speaking about a "kill" setting for Data, even though the android likely wouldn't be extinguished at lower settings of the phaser's kill range.