Digitizing readback waveform for testing hard disc drives

Details Digitizing readback waveform for testing hard disc drives Digitizing readback waveform for testing hard disc drives

1999-06-11

2002-09-24

Young, Brian (Department: 2819)

Coded data generation or conversion

Analog to or from digital conversion

C360S031000, C360S135000

Reexamination Certificate

active

06456213

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of mass storage devices. More particularly, the present invention relates to testing hard disc drives during the manufacturing process.
BACKGROUND OF THE INVENTION
One of the key components of any computer system is a place to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are a disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved from and written to the disc surface. A microprocessor controls most of the operations of the disc drive, including passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically housed within the slider. The slider is a small ceramic block that is passed over the disc in a transducing relationship with the disc. The small ceramic block, also referred to as a slider, is usually aerodynamically designed so that is flies over the disc. Most sliders have an air bearing surface (“ABS”), which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface, causing pressure, which forces the head away from the disc. At the same time, the air rushing past the depression in the air bearing;surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring that produces a force on the slider directed toward the disc surface. The various forces equilibrate so that the slider flies over the surface of the disc at a particular fly height. The fly height is the thickness of the air lubrication film or the distance between the disc surface and the transducing head. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the memory disc. Disc drive systems read and write information stored on tracks on memory discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disc, read and write information on the memory discs when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disc. The transducer is also said to be moved to a target track. As the memory disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the memory disc. Similarly, reading data from a memory disc is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disc. To write to or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disc drives, the tracks are a multiplicity of concentric circular tracks. In other disc drives, a continuous spiral is one track on one side of a disc drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
In hard drive manufacturing environments, one of the most significant criteria that determines drive performance is the soft error rate of the drive. In order to ensure that the drive satisfies soft error rate criteria, a number of conventional test procedures have been implemented in the process flow.
According to one conventional test procedure, a new drive is tested on a head parametric tester at the beginning of a test process to screen out bad heads. This screening process helps ensure that only drives with good heads pass to the next stage, at which a drive optimization test is performed. Finally, an error rate test is performed. In this procedure, therefore, the head parametric testing stage filters out drives with bad heads to ensure that most of the drives that pass it will also pass the error rate test. While quality control is reasonable using this test procedure, the head parametric test increases manufacturing costs significantly.
In another conventional test procedure, a new drive is initially optimized during the drive optimization test, and head parametric testing is omitted. After the drive optimization test, the error rate test is performed. In this procedure, drives with bad heads are screened during the error rate test. While this procedure is also effective in controlling quality, substantial overhead in testing time is introduced as potentially many drives with bad heads are unnecessarily subjected to error rate testing. In many cases, other screening procedures, such as head parametric testing, would have prevented these drives from being subjected to error rate testing.
The condition of the drive head can also be determined by studying a readback waveform from the hard drive preamplifier. This approach involves the use of an external instrument, such as an oscilloscope. While using external instruments is suitable for laboratory or bench testing, it is not suitable for mass production environments, which require testing of a large number of drives.
Accordingly, a need continues to exist for a cost-efficient, accurate, and reliable method of determining the condition of the drive head.
SUMMARY OF THE INVENTION
The present invention is related to methods and arrangements for solving the above-mentioned problems by facilitating examination of a digitized readback waveform from the drive itself.
By using this readback waveform to characterize the drive, the condition of the head can be ascertained inexpensively and accurately. In addition, this technique is easily implemented by modifying the existing drive test firmware in the manufacturing environment. Accordingly, no new system hardware is required to implement the present invention.
One particular embodiment is directed to a method for reconstructing an analog readback signal for use in testing a disc drive. This method includes the steps of digitizing a waveform generated within a read channel arrangement to produce digitized waveform data and determining the analog readback signal as a function of the digitized waveform data. Another embodiment is directed to an information handling system implementing this method.
According to still another embodiment of the present invention, a disc drive has a base, a disc rotatably attached to the base, and an actuator attached to the base. One end of the actuator has a transducer, and the other end of the actuator has a voice coil that forms a portion of a voice coil motor. A read channel arrangement is configured to digitize a waveform generated within itself to produce digitized waveform data and to determine an analog readback signal as a function of the digitized waveform data.
These and various other features as well as advantages that characterize the present invention will be apparent upon reading the following detailed description and reviewing the associated drawings.


REFERENCES:
patent: 5341249 (1994-08-01), Abbott et al.
patent: 5416646 (1995-05-01), Shirai
patent: 5422760 (1995-06-01), Abbott et al.
patent: 5430584 (1995-07-01), Peterson
patent: 5450253 (1995-09-01), Seki
patent: 5465343 (1995-11-01), Henson et al.
patent: 5559983 (1996-09-01), Masood
patent: 5586306 (1996-12-01), Romano et al.
patent: 5771131 (1998-06-01), Pirzadeh
patent: 5801896 (1998-09-01), Freitas
patent: 5860089 (1999-01-01), Ishii
patent: 5978

Affiliated with

Also associated with

Rating

Digitizing readback waveform for testing hard disc drives does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Digitizing readback waveform for testing hard disc drives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digitizing readback waveform for testing hard disc drives will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2891394