Patent ID: 7623315

Claim:
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.