Setting an operating bias current for a magnetoresistive head by computing a target operating voltage
AssigneeWestern Digital (Fremont), LLC
InventorsCurtis V. Macchioni, Jonas A. Goode, Matthew R. Gibbons, Tao Pan, Andrei F. Khapikov
Life of this patent
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Abstract
A disk drive is disclosed having a disk, and a head actuated over the disk, the head comprising a magnetoresistive (MR) element. Control circuitry within the disk drive sets an operating bias current for the MR element by computing a target voltage for the MR element, applying a bias current to the MR element, measuring a voltage across the MR element corresponding to the bias current, and adjusting the bias current applied to the MR element until the measured voltage substantially equals the target voltage.
Claims16
A disk drive comprising:
- a disk;
- a head actuated over the disk, the head comprising a magnetoresistive (MR) element;
- and
- control circuitry operable to set an operating bias current for the MR element by:
- computing a target voltage for the MR element;
- applying a bias current to the MR element;
- measuring a voltage across the MR element corresponding to the bias current;
- and
- adjusting the bias current applied to the MR element until the measured voltage substantially equals the target voltage,
- wherein the control circuitry computes the target voltage using a function comprising a DC offset, and the control circuitry is further operable to set the operating bias current for the MR element by:
- determining a first DC offset of the function corresponding to a first ambient temperature;
- determining a second DC offset of the function corresponding to a second ambient temperature;
- measuring an ambient temperature of the disk drive;
- and
- adjusting the DC offset of the function in response to the first DC offset, the second DC offset, and the measured ambient temperature.
A disk drive comprising:
- a disk;
- a head actuated over the disk, the head comprising a magnetoresistive (MR) element;
- a heater for heating the MR element in order to adjust a fly-height of the MR element;
- and
- control circuitry operable to set an operating bias current for the MR element by computing a target voltage for the MR element according to:
- b0+(b1·R)+(b2·W)+(b3·R·W)+(b4·Ftemp)+(b5·Ftemp·R)
- where:
- R is a resistance estimate for the MR element;
- Ftemp is a measured ambient temperature of the MR element;
- W is a heater power of the heater;
- and
- b0-b5 are coefficients.
A method of setting an operating bias current for a magnetoresistive (MR) element of a disk drive, the disk drive comprising a disk, and a head actuated over the disk, wherein the head comprises the MR element, the method comprising:
- computing a target voltage for the MR element;
- applying a bias current to the MR element;
- measuring a voltage across the MR element corresponding to the bias current;
- and
- adjusting the bias current applied to the MR element until the measured voltage substantially equals the target voltage,
- wherein the target voltage is computed using a function comprising a DC offset, further comprising:
- determining a first DC offset of the function corresponding to a first ambient temperature;
- determining a second DC offset of the function corresponding to a second ambient temperature;
- measuring an ambient temperature of the disk drive;
- and
- adjusting the DC offset of the function in response to the first DC offset, the second DC offset, and the measured ambient temperature.
A method of setting an operating bias current for a magnetoresistive (MR) element of a disk drive, the disk drive comprising a disk, and a head actuated over the disk, wherein the head comprises the MR element, the method comprising:
- heating the MR element according to a heating parameter in order to adjust a fly-height of the MR element;
- and
- setting the operating bias current for the MR element by computing a target voltage for the MR element according to:
- b0+(b1·R)+(b2·W)+(b3·R·W)+(b4·Ftemp)+(b5·Ftemp·R)
- where:
- R is a resistance estimate for the MR element;
- Ftemp is a measured ambient temperature of the MR element;
- W is a heater power of the heater;
- and
- b0-b5 are coefficients.
Dependencies are inferred from the claim text.