An electric phaser for dynamically adjusting the phase of a camshaft relative to a crankshaft with a split ring planetary drive. The split ring planetary drive including: a sun gear driven by a motor, a plurality of planetary gears with stop teeth, a first ring gear driven by the crankshaft, and a second ring gear rotatable with the camshaft. Either the first or second ring gears each include a first and a second stop. When the stop teeth of the planetary gears interacts with the first stop or the second stop on either the first or second ring gears, rotation of the phaser further in the first direction or the second direction towards the first or second stops is halted.