Browse Prior Art Database

Adaptive Magnetic Write Width Control

IP.com Disclosure Number: IPCOM000110271D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 92K

Publishing Venue

IBM

Related People

Kurachi, K: AUTHOR [+4]

Abstract

Disclosed is a technique of increasing track density of disk drive by adaptive control of magnetic write width at each head in each drive. Write width depends upon write current. If write current increases, the write width increases, too. If write current decreases, the write width decreases, too. Track width is determined by considering sufficient design margin against its write width variation and track misregistration (TMR) variation in volume production.

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Adaptive Magnetic Write Width Control

       Disclosed is a technique of increasing track density of
disk drive by adaptive control of magnetic write width at each head
in each drive.  Write width depends upon write current.  If write
current increases, the write width increases, too.  If write current
decreases, the write width decreases, too.  Track width is determined
by considering sufficient design margin against its write width
variation and track misregistration (TMR) variation in volume
production.

      By choosing optimum write current, that is, optimum write width
for each head in each single drive, high track density in the disk
drive is attained because unnecessary design margin for track width
can be eliminated.

      The algorithm for optimizing the write current is given below.

      Lower limit L for write current I:
(1)  As shown in Fig. 1, at first, a test signal is written on a
track N with a certain write current I which makes a certain write
width on the track N at both sides of the centerline of the Track N.
(2)  Then, the test signal is read where the head is away from the
centerline of the track N with a certain amount of offtrack position.
(3)  If the read test signal meets a certain criteria when measuring
error rate of the read test signal, the write current I is above the
Lower limit L.  If the read test signal does not meet the criteria,
try again steps (1) (2) and (3) with increased write current I until
the read te...