Adaptive dampening of thermal asperity events in disc drives

A disc drive having a basedeck supporting a spindle motor assembly with at least one axially aligned rotatable disc surface, a head stack assembly with at least one magneto-resistive read/write head positionably adjacent the rotatable disc surface providing a signal read from the rotatable disc surface, and a printed circuit board assembly with a read/write channel communicating with the magneto-resistive read/write through a preamplifier, the printed circuit board assembly comprising:

• a variable gain amplifier communicating with the preamplifier for adjusting the signal provided by the magneto-resistive read/write head for use by the read/write channel;
• a dampening capacitor in parallel with the variable gain amplifier for filtering the signal provided by the magneto-resistive read/write head;
• an amplitude range value determined from a baseline signal provided by the magneto-resistive read/write head for use in determining an amount of dampening resistance to apply to the signal provided by the magneto-resistive read/write head;
• a plurality of first resistors connected serially and communicating with the amplitude signal range value for use in separating the amplitude signal range value into a plurality of equal amplitude signal portions, to determine the amount of dampening resistance to apply to the signal provided by the magneto-resistive read/write head;
• a plurality of comparators, wherein each comparator is connected to one of the plurality of first resistors and used in determining the amount of dampening resistance to apply to the signal provided by the magneto-resistive read/write head;
• a plurality of switches each with an attached second resistor, each switch connected in series with its associated second resistor and responding to one of the plurality of comparators to switch in the second resistor in response to a signal from its associated comparator, each switch responding to its associated comparator by switching in its associated second resistor to contribute to an amount of dampening resistance applied to the signal provided by the magneto-resistive read/write head;
• and
• a plurality of reference voltages, each of the plurality of reference voltages associated and communicating with one of the plurality of comparators, each of the plurality of comparators comparing its associated reference voltage to one of the equal amplitude signal portions to determine activation of its second resistor to contribute to the amount of dampening resistance applied to the signal provided by the magneto-resistive read/write head to dampen the signal provided by the magneto-resistive read/write head.

A disc drive having a basedeck supporting a spindle motor assembly with at least one axially aligned rotatable disc surface, a head stack assembly with at least one magneto-resistive read/write head positionably adjacent the rotatable disc surface providing a signal read from the rotatable disc surface, and a printed circuit board assembly with a read/write channel communicating with the magneto-resistive read/write through a preamplifier, the printed circuit board assembly comprising:

• a variable gain amplifier communicating with the preamplifier for adjusting the signal provided by the magneto-resistive read/write head for use by the read/write channel;
• a dampening capacitor in parallel with the variable gain amplifier for filtering the signal provided by the magneto-resistive read/write head;
• and
• an n-channel enhancement metal on silicon field effect transistor attached in parallel with the dampening capacitor provide a dampening resistance for dampening down the signal provided by the magneto-resistive read/write head by steps for dampening the signal provided by the magneto-resistive read/write head.