Burroughs, Inc.

Sidney J Schwartz

Wilbur T Layton

Farooq M Quadri

John C Unger

Chung H Hsin

Chung-Herng Hsin

Ling G Chow

This disclosure relates to a bias field magnet for magnetic bubble memory devices which is formed of alternating layers of hard and soft ferrite powders which are subsequently fired together to form a magnetic structure. A particular embodiment of the present invention resides in a structure where the hard ferrite layer is encased on both its top and bottom surfaces by soft ferrite layers.

Method of fabricating magnets

A method of forming detector and dummy detector pair(s) of magnetoresistive elements on a bubble memory chip, with detector and dummy detector each having a balancing resistance network comprising parallel spaced apart end-connected lines of resistive material with the transverse legs (rungs) spaced between said parallel lines to form a ladder in-line (electrically) between the detector and pads for selectively balancing the pair(s), and for disconnecting certain rungs of the spaced apart end connected lines, if necessary, to change the path of current flow through the ladder and thus vary the resistance through the ladder. The product formed by the method comprises on-chip magnetoresistive detector element pair(s) including balancing resistance ladders, coupled in the current paths of the magnetoresistive elements, and having portions which can be selectively disconnected to change resistance of the ladder to balance the bridge network.

On-chip method of balancing memory detectors and balanced detectors

A bubble (domain) generator comprising a pair of relatively long elements of suitable magnetic material, such as permalloy, separated by a narrow gap, near which bubbles will be generated in the bubble film by the combined effect of local in-plane and perpendicular magnetic field components to assist in nucleation. In one embodiment, the gap is formed straight by spaced apart edges between the elements and, in another embodiment, the gap is formed to define an apex by V-shaped by complementary tapered spaced apart edges between the elements. Both embodiments may have their gap edges brought close to the bubble film and may have a current carrying hairpin loop conductor substantially surrounding the gap to assist in nucleation.

Bubble nucleator

A passive annihilator comprising an annihilator element in the form of a spiral located at the end of a path of propagate elements whereby bubbles, entering the spiral element in response to the rotating in-plane magnetic field, will follow the spiral path to its center, and any subsequent bubbles, in a stream of bubbles, entering the spiral will help hold the prior bubble captive in the spiral. The final bubble in a bubble stream under high magnetic bias conditions will be annihilated near the spiral center while the final bubble under low magnetic bias conditions will circulate in response to the in-plane rotating field indefinitely in the spiral, but is not free to escape, and will be annihilated by the entry of new bubbles from a subsequent bubble stream.

Passive annihilator

In a magnetic bubble (domain) memory chip, transfer gating circuits of propagate elements oriented to be responsive to different phases of in-plane rotating magnetic field are operated by a single conductor which is subjected to current pulses during a specific phase of the rotating field cycle to transfer bubbles onto different bubble paths. The transfer gates perform their gating function only when a control current pulse occurs during a specific phase of the rotating field cycle and are unresponsive to the current pulses at other phase times on the same conductor which actuate other gates.

Phase controlled gating

Replicate/swap gating circuitry comprising separate gates oriented to be responsive to different phases of an in-plane magnetic field for transferring data to and from an adjacent storage loop in a bubble memory, said gate being formed of magnetic domain propagate elements arranged in propagation paths to perform several independently operable gating functions by a single current conductor on application of current pulses at selected phases of the rotating in-plane magnetic field.

Phase controlled replicate/swap gate for bubble memories

An on-chip magnetic bubble decoder comprising a plurality of sequentially operated gates oriented to be responsive to different phases of the rotating in-plane magnetic field and connected to a conductor which is pulsed at the selected phase of the cycle to transfer bubbles from one track onto different tracks to be propagated therefrom. In its simplest form, one gate oriented to be operated during the phase 2 time of the cycle and a second gate oriented to be responsive to the phase 1 time of the cycle, all operable by a single conductor, thus form a four output decoder with two gates and a single conductor. A second conductor controls a third gate which modulates the bubble stream to control the data being decoded.Further embodiments of the invention include 8 output decoder (2 data bits decoded into 1 of 4 paths) with only two conductors for activating the gates and a 1 of 16 output decoder with 2 conductors for decoding and a third for data control. In another embodiment the 16 output decoder is arranged with the data control gates located at the decoder output to reduce write cycle latency.

Phase controlled decoder for bubble memories

A bubble memory organization with a plurality of storage loops in-plane folds allows the selective spacing of transfer and other functional elements from each other eliminating crowded conditions at loop ends. This permits the selective placement of the functional elements for the maximization of operating margins. This can also lead to reduced current requirements because passive replicate elements may be used, to reduced transfer line impedances, to reduced number of conductor lines and to a reduced number of transfer points per memory array. For the designs where passive replication is chosen, reliability is improved due to the reduction in current density to levels further below the conductor electromigration thresholds.

Bubble memory chip organization-folded loop type

Circuitry for use in bubble memory propagation wherein field drive coils receive energy from an energy storage device (capacitor) through a plurality of selectively located and timed switches. A basic digitally controlled switching arrangement is illustrated in matrix form and, in one embodiment, one capacitor with two voltage sources and, in another embodiment, two capacitors and a single voltage source are utilized. Selective timing of the opening and closing of the switches provides a digitally controlled series of 1/2 sine wave current pulses to meet operating requirements for bubble propagation. Additional variations of the selective timing of switch opening and closings are used to elongate the start and stop pulses to provide better operating margins for these events. Field rotation in either clockwise, or counter-clockwise, or a mix of rotational senses is readily achieved under digital control.

Bubble memory coil drive circuit

A package having bubble memory components comprising an innerassembly of bubble memory chips surrounded by spaced orthogonally oriented drive coils, a printed circuit board having a rigid support portion for the chips and a flexible portion containing conductors for direct interchip communication and for direct connection to the outside world, means in the form of tapers of controlled thermally conductive material for assisting in controlling the temperatures of the bias magnets and for providing a magnetic gradient for bubble propagation, thermal compliant members, and flexible heat conductors which together with the tapers, manage the heat within the package.

Magnetic bubble package

In a bubble memory system having a detector device for sensing the presence or absence of magnetic bubbles in a bubble stream and producing an output signal accordingly which is sensed by a differential sense amplifier having a clamp circuit to select the voltage level with which the signal is to be compared at a sampling time and a strobe circuit for sampling the signal at the preselected time, a dynamic input signal offset for enhancing the signal-to-noise factor at the input to the sense amplifier so that a signal representing an absence of a bubble is clearly distinguishable over a bubble presence signal. This invention disclosed is disclosed as operable with a d.phi./dt or magnetoresistive bridge type detectors and comprises means for shifting the signal level negatively by providing a negative going pulse just after the time the clamp circuit is released and while the signal is being sampled. In one embodiment of this invention, the negative going pulse is applied inductively and in another embodiment the negative going pulse is applied capacitively. The point of implementation of the dynamic input signal may be either within the bubble device itself or contained in a circuit board to which both the bubble device and sense amplifier interfaces.

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Vista, CA, United States of America

Sidney J Schwartz