Disk drive with head thermal fly-height actuator and controller for compensation of write head expansion

Abstract

The invention is a disk drive with a thermal fly-height actuator and a fly-height controller that compensates for exponential write pole protrusion during a write operation. The fly-height controller includes fly-height control logic that controls a single digital-to-analog converter (DAC) that outputs a voltage to drive the heater. Prior to writing, the heater is at the heater power value (HPV) required to maintain the read head at the desired fly-height (Read-HPV). At the initiation of writing the fly-height control logic inputs a new HPV to the DAC to reduce the heater power to begin the compensation. A new and successively reduced HPV is input to the DAC for each servo-identification (SID) mark, during which writing is prevented. When the DAC output voltage approaches the voltage corresponding to the desired write-head fly-height, the method is done.