Patent Application
20080088962
Disclosed is a hard disk drive that is capable of inhibiting a write operation when a varying fly height is detected. The disk drive includes a filter circuit that filters a read signal read from a disk. By way of example, the filter circuit may be a low pass filter with a frequency range of 40 to 300 KHz. If the flying height is varying, for example in response to vibration in the drive, the read signal will have a low frequency component. The low pass filter will output the low frequency component. The existence of the low frequency component will cause the disk drive to inhibit a write operation on the disk. In this manner the drive does not perform a write operation while the head is undergoing mechanical resonance.
Referring to the drawings more particularly by reference numbers,
The disk drive 10 may include a plurality of heads 20 located adjacent to the disks 12. As shown in
Referring to
The hard disk drive 10 may include a printed circuit board assembly 38 that includes a plurality of integrated circuits 40 coupled to a printed circuit board 42. The printed circuit board 40 is coupled to the voice coil 32, heads 20 and spindle motor 14 by wires (not shown).
The read/write channel circuit 62 is connected to a controller 64 through read and write channels 66 and 68, respectively, and read and write gates 70 and 72, respectively. The read gate 70 is enabled when data is to be read from the disks 12. The write gate 72 is to be enabled when writing data to the disks 12. The controller 64 may be a digital signal processor that operates in accordance with a software routine, including a routine(s) to write and read data from the disks 12. The read/write channel circuit 62 and controller 64 may also be connected to a motor control circuit 74 which controls the voice coil motor 36 and spindle motor 14 of the disk drive 10. The controller 64 may be connected to a non-volatile memory device 76. By way of example, the device 76 may be a read only memory (“ROM”) that contains instructions that are read by the controller 64.
The read channel 58 may include a low pass filter 80 connected to the read data channel 54 of the preamp 52. The low pass filter 80 filters the incoming read signal read from the disks 12. By way of example, the low pass filter 80 may pass thru frequencies between 40 to 300 KHz. It has been found that any mechanical modulation of the heads and resultant variations of the flying height will typically be in this range. The output of the low pass filter 80 can be provided to the controller 64. If the output is indicative of head modulation then the controller 64 may inhibit any subsequent write operation of the drive 10.
It may be desirable to read the disk before each and every write operation to determine whether the head(s) flying height is varying. By inhibiting the write operation during variations in the fly height the drive reduces the probability of writing invalid data.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.
For example, although the low pass filter is shown in the read channel it is to be understood the filter could a separate circuit, or part of another circuit such as the preamp, or the controller. Additionally, although the output of the filter is described as being analyzed by the controller, the read channel or a separate circuit could analyze the output and inhibit the write gate.
