Circuits, systems, and methods for capacitive fly height measurement
AssigneeMarvell International Ltd.
InventorParvis Rahgozar
Life of this patent
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Abstract
Circuitry, systems, and methods for measuring the fly height of a read/write head in a magnetic data storage system. The circuitry generally includes a measurement circuit configured to determine an electrical current of a periodic signal applied to the read/write head, wherein the periodic signal has a generally constant voltage slew rate, and a fly height converter configured to produce an output signal based on a value of the electrical current, wherein the output signal corresponds to the fly height. The present invention advantageously provides for electronically measuring the fly height of a read/write head in situ in a magnetic storage system. The sensed fly height may then be used by the system to control fly height actuation.
Claims16
A circuit for measuring a fly height in a magnetic data storage system, wherein the fly height comprises a distance between a read/write head and a surface of a storage medium, the circuit comprising:
- a measurement circuit configured to determine an electrical current of a periodic signal having a generally constant voltage slew rate applied to the read/write head, the measurement circuit comprising:
- a comparing circuit configured to compare a voltage at the read/write head to a ground potential or reference voltage and generate a comparison output comprising one or more pulses in response to the periodic signal when the voltage at the read/write head substantially differs from the ground potential or reference voltage,
- a current generator coupled to the read/write head, the current generator being configured to produce a current output in response to a number of the one or more pulses, and
- an adjustment circuit comprising a counter configured to count the one or more pulses of the comparison output, the adjustment circuit being configured to adjust the current generator in response to the comparison output;
- and
- a fly height converter configured to produce an output signal based on a value of the electrical current, wherein the output signal corresponds to the fly height.
A digital storage system, comprising:
- a read/write head;
- a storage medium;
- a measurement circuit configured to determine an electrical current of a periodic signal having a generally constant voltage slew rate, the measurement circuit comprising:
- a comparison circuit configured to compare a voltage at the read/write head to a ground potential or reference voltage and generate a comparison output comprising one or more pulses in response to the periodic signal when the voltage at the read/write head substantially differs from the ground potential or reference voltage, wherein the periodic signal is coupled to the read/write head;
- a current generator coupled to the read/write head, the current generator being configured to produce a current output in response to a number of the one or more pulses;
- and
- an adjustment circuit comprising a counter configured to count the one or more pulses of the comparison output, the adjustment circuit being configured to adjust the current generator in response to the comparison output;
- a fly height converter configured to produce a fly height output signal based on a value of the electrical current, wherein the output signal corresponds to a distance between the read/write head and a surface of the storage medium.
A method of measuring a fly height in a data storage system, wherein the fly height comprises a distance between a read/write head and a surface of a storage medium, the method comprising:
- generating a periodic signal with a generally constant voltage slew rate;
- applying the periodic signal to the read/write head;
- comparing a voltage at the read/write head to a ground potential or reference voltage to generate a comparison output;
- applying a counter-current to the read/write head in response to the comparison output;
- determining a combined electrical current of the periodic signal and the counter-current, wherein determining the electrical current of the periodic signal comprises determining an electrical current at the read/write head and adjusting the counter-current until the voltage at the read/write head substantially equals the ground potential or reference voltage;
- and
- calculating a value corresponding to the fly height from the electrical current.
Dependencies are inferred from the claim text.