Browse Prior Art Database

Start Stop Holding Field

IP.com Disclosure Number: IPCOM000089409D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Pugh, EW: AUTHOR

Abstract

It has generally been found to be desirable to use an in-plane holding field with bubble devices in order to assure no loss of information during start-stop operation. This can be accomplished by retaining a small DC current in the drive coils, following shutdown, in the direction of the rotating field at the time the rotation is stopped. However, for power-off shutdown, this field would have to be supplied by a battery in order to assure information retention.

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Start Stop Holding Field

It has generally been found to be desirable to use an in-plane holding field with bubble devices in order to assure no loss of information during start-stop operation. This can be accomplished by retaining a small DC current in the drive coils, following shutdown, in the direction of the rotating field at the time the rotation is stopped. However, for power-off shutdown, this field would have to be supplied by a battery in order to assure information retention.

This problem is now generally solved by tipping the bubble chip in the permanent-magnet-supplied bias field so that there is a small in-plane component in addition to the large perpendicular component. This in-plane field component (defined here to be the +y direction), when added to the rotating field of the drive coils, results in a larger drive field in the +y than the -y direction; and drive fields in the +x and -x directions are in between these values. The minimum drive field is typically increased by an amount which is approximately equal to the size of the holding field, the nominal drive field is usually increased by a somewhat smaller amount, and the operating margins for any given drive field are reduced. The increased power requirement and the loss of margin are both undesirable.

To correct these problems, a DC current is applied to the drive coils simultaneously with the AC components. The DC component should be initiated simultaneously with initiation of bubble propag...