An apparatus for driving a display includes a shift register, a first latch unit, a second latch unit, a data comparison unit and a level select unit. A controller may selectively activate the magnetic feature to magnetically oscillate and produce a radio frequency signal proximal the write pole on an air bearing surface. When the output voltage of the charge pump circuit increases the current in the second current generator increases, the current flowing into the current controlled oscillator decreases, the frequency of the clock signals supplied to the charge pump circuit decreases, and the output voltage of the charge pump circuit decreases.