Browse Prior Art Database

Flexible Control of Write Current

IP.com Disclosure Number: IPCOM000122476D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 70K

Publishing Venue

IBM

Related People

Kosuge, O: AUTHOR [+3]

Abstract

Disclosed is a YIELD improvement technique for HDD (Hard Disk Drive). HDD, has several read/write HEADs, and "fail or pass" highly depends on the worst HEADs. So improvement of the worst HEAD is an important for production YIELDs.

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Flexible Control of Write Current

      Disclosed is a YIELD improvement technique for HDD (Hard
Disk Drive).  HDD, has several read/write HEADs, and "fail or pass"
highly depends on the worst HEADs. So improvement of the worst HEAD
is an important for production YIELDs.

      A good HDD can read written data correctly.  However, if WRITE_
CURRENT is not optimum, SER (Soft Error Rate) becomes high.  In other
words, the possibility that the HDD cannot read written data
correctly becomes high.  So WRITE_CURRENT is an important parameter
for HDD SER.
      1)   Optimum WRITE_CURRENT highly depends on the HEAD/DISK
combination. Some WRITE_CURRENT is optimum for some HEAD/DISK
combinations.
           But it is not optimum for other HEAD/DISK combinations.
And, since one HDD has several HEAD/DISK combinations, "fail or pass"
highly depends on the worst combination. HDD is judged "fail" by only
one bad combination.
      2)   Optimum WRITE_CURRENT depends on HEAD/DISK velocity (see
Fig. 1). HEAD/DISK velocity depends on the head position in the
radius direction (slower in the inner side and faster in the outer
side).
           So optimum WRITE_CURRENT depends on the head position.
      3)   General optimization
           - Reduced WRITE_CURRENT is used for the inner-side
position.
           - Increased WRITE_CURRENT is used for the outer-side posi
tion.
           - The cylinder where WRITE-CU...