Drive electronics employing unipolar last write for improved magnetic stability

A magnetic media drive, comprising:

• a housing;
• magnetic media mounted in the housing;
• means for moving the magnetic media;
• a combined read-write head;
• means mounted in the housing for supporting the combined read-write head in a transducing relationship with respect to the magnetic media in response to movement of the magnetic media;
• a polarity detector that provides a polarity signal indicating the polarity of a last write pulse of a set of write pulses;
• and
• a write head polarity controller responsive to the polarity signal, the write head polarity controller being configured to output a pulse activation signal if the last write pulse of the set of write pulses does not have a designated polarity, the pulse activation signal causing the write head to be pulsed with one or more additional pulses of said designated polarity.

A disk drive, comprising:

• a housing;
• a rotatable magnetic disk mounted in the housing;
• means for rotating the magnetic disk;
• a combined read-write head;
• a support, including a slider, mounted in the housing for supporting the combined read-write head in a transducing relationship with respect to the magnetic disk in response to rotation of the magnetic disk;
• a polarity detector that provides a polarity signal indicating the polarity of a last write pulse of a set of write pulses;
• and
• a write head polarity controller responsive to the polarity signal, the write head polarity controller being configured to output a pulse activation signal if the last write pulse of the set of write pulses does not have a designated polarity, the pulse activation signal causing the write head to be pulsed with one or more additional pulses of said designated polarity.

A monolithic application specific integrated circuit (ASIC), comprising:

• one or more circuits, at least one of the circuits comprising drive electronics for a combined read-write head disk drive, including:
• a polarity detector that provides a polarity signal indicating the polarity of a last write pulse of a set of write pulses;
• and
• a write head polarity controller responsive to the polarity signal, the write head polarity controller being configured to output a pulse activation signal if the last write pulse of the set or write pulses does not have a designated polarity, the pulse activation signal causing the write head to be pulsed with one or more additional pulses of said designated polarity.