Seagate Technology Incorporated

DetHau Wu

Edmun ChianSong Seng

UttHeng Kan

LinNah Lim

Utt Heng Kan

HonYeong Mak

Apparatus and methods are disclosed that regulate head fly height so as to compensate for variation in height of a disk surface. An exemplary apparatus includes a circuit that detects disk height variation in response to variation in the gain of a variable gain amplifier, within an automatic gain control loop, that amplifies a read signal as the head reads from the disk surface. The circuit regulates the head fly height so as to compensate for the detected variation in disk height.

Fly height compensation using read gain control loop

A computer process establishes data frequencies for recording data in zones of a zone bit recording medium in a disc drive. At least three data points are identified for each zone correlating data frequencies and corresponding bit error rates, and a slope of a curve between each two data points is calculated. The slopes are averaged, and the data frequency is calculated based on the average slope. If a difference between the average and default slopes exceeds a first threshold value, or if a spread of the slopes exceeds a second threshold value, the data frequency is calculated based on the average slope and the default slope. In one embodiment, each of the three data points is generated by recording data in the zone at each of three selected data frequencies, reading the recorded data, and calculating bit error rates based on the recorded and read data.

Calculation of data frequencies in recording media

A channel adjustment control adjusts a channel to reduce bit error rate in a disc drive. Variable gain register settings are read and compared to filter characteristics to provide an operational boost register setting for an adjustable gain amplifier in the channel. An operational pole register setting is provided based on the operational boost register setting and known parameters of the adjustable low pass filter. Low and high frequency data patterns are applied while the channel adjustment control reads the variable gain register settings.

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Singapore, Singapore

DetHau Wu