ELECTRONIC ABATEMENT OF THERMAL INTERFERENCE IN (G)MR HEAD OUTPUT SIGNALS

Abatement methods are described for Thermal Interference (TI) events e ncountered in hard disk drives using airbearing exposed (G)MR sensors, Two classes of TI events are analyzed; ''thermal asperities'' resulti ng from frictional heating by asperity-sensor contacts, and ''baseline wander'' caused by increased cooling when the sensor passes over near contacts. Countermeasures are discussed that can be taken at the head level, at the head-disk interface level, at the channel electronics l evel and at the system level. Various forms of electronic abatement ar e presented. Several methods for generating TI flags are shown, Circui try for ''cloaking'' the TI events is discussed, Since TI events are a dditive to the data signal, the best results are obtained with subtrac tive restoration methods. A circuit implementation (Asperity Reduction Circuit) is presented and measured results are discussed.