JPS5842552B2 - magnetic bubble memory device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic bubble memory device, particularly to improving its operating characteristics, and more particularly to improving the phase margin of operating pulses of a magnetic bubble memory chip.

Generally, a magnetic bubble memory chip forming a part of a magnetic bubble memory device operates under an external magnetic field as shown in FIG.

That is, in the figure, 1 is a magnetic bubble memory chip, and for convenience of explanation, the surfaces of this chip 1 are x, y
, 'zZ axis direction symbols are attached.

HB is an external DC magnetic field that acts perpendicularly to the plane of the chip 1 (parallel to the Z axis) and is called a bias magnetic field.

The magnitude of this bias magnetic field HB is set to an appropriate value determined by the material characteristics of the bubble magnetic film of chip 1.
Normally, it is set to a value before and after the bubble demagnetization field HO.

In addition, the direction of this bias magnetic field HB is +Z in the example shown in the figure.
Although it is set in the Z-axis direction, it may also be in the -Z-axis direction.

HR is an external rotating magnetic field that rotates within the plane (xy plane) of the chip 1, and the magnitude of this rotating magnetic field HR is usually 3
It is set to about 00e to 500e.

Further, although the rotating direction of the rotating magnetic field HR is counterclockwise in the example shown in the figure, it may also be clockwise.

In order to operate such a chip 1, these two types of external magnetic fields, namely, the bias magnetic field HB and the rotating magnetic field HR are required.
In addition to this, various operating pulse currents (not shown) are applied to the chip 1.

In this case, the bias magnetic field HB is a magnetic field that is constantly applied regardless of whether the chip 1 is operating as a memory or not.

On the other hand, the rotating magnetic field HR is a magnetic field that is applied only during memory operation, and is a magnetic field that becomes zero during non-operation.

That is, the rotating magnetic field HR repeats start/stop (St/Sp) operations in synchronization with the memory operation.

The direction of the rotating magnetic field HR at St/Sp is determined to be a certain fixed direction, and although this certain direction is the +x-axis direction in the example of FIG. 1, it may be other directions.

In the following explanation, the bias magnetic field H as shown in FIG.
The direction of B is the +x axis direction, the rotation direction of the rotating magnetic field HR is counterclockwise, and the start/stop (St/Sp)
The direction is the +x axis direction.

Further, the reference 0 degree for the phase θ of the operating pulse current (timing at which the operating pulse current flows) is selected when the rotating magnetic field HR faces the St/Sp direction.

Even in this case, the film properties are not lost.

The magnetic bubble memory device configured in this manner has the following problems.

First, Figure 2 shows an example of the operating characteristics of a magnetic bubble memory chip, that is, the phase θ characteristics of the operating pulse current.The horizontal axis represents the phase θ, and the vertical axis represents the bias magnetic field strength. This is the result of finding a stable operating region.

In this case, the phase θ is a value representing the timing at which the operating pulse current starts flowing in the direction of the rotating magnetic field HR.

In the same figure, the region sandwiched by the two curves HUHL is the stable operation region, and the phase θ is from (θ1.θ2)
・If it is within the range, the range of the bias magnetic field that can operate stably will not decrease.

Here, θ1 is referred to as the lower limit value of the pulse phase, Q2 is referred to as the upper limit value of the pulse phase, and JMθ (θ2 to θ1) is referred to as the phase margin.

In this case, in the example shown in the figure, JMθ=17.5 degrees,
The wider the phase margin JMθ, the better the characteristics.

FIG. 3 is an example of the results obtained by incorporating the chip shown in FIG. 2 into a magnetic bubble memory device many times and determining the reproducibility of the lower limit value θ1 and upper limit value θ2 of the pulse phase θ.

In the same figure, as it is clear from this figure, the lower limit value Q0 and upper limit value θ2 of the pulse phase have a variation of approximately ±4 degrees, so the apparent phase margin JM'θ is 17
．． 5 degrees - 8 degrees = 9.5 degrees, which is half the phase margin shown in FIG.

In this way, the conventional magnetic bubble memory device has a pulse phase margin AMθ of about 17 degrees in a single chip, but when incorporated into a memory device, the lower limit value θ1 and upper limit value θ2 vary, and the apparent phase margin JM'θ is approximately 8
The problem was that the degree of variation (the degree of variation) decreased by half to about 9 degrees.

Therefore, an object of the present invention is to reduce the width of variation in the upper limit value θ2 and lower limit value θ1 of the pulse phase θ after the chip is incorporated into a memory device, and to reduce the width of the variation in the upper limit value θ2 and lower limit value θ1 of the pulse phase θ after the chip is incorporated into a memory device.
An object of the present invention is to provide a magnetic bubble memory device in which the amount of decrease in θ is close to zero.

In order to achieve this object, the magnetic bubble memory device according to the present invention is such that the median value of the phase margin JMθ of the operation pulse is set to a certain special value.

Hereinafter, a magnetic bubble memory device according to the present invention will be described in detail with reference to the drawings.

FIGS. 4a and 4b are sectional views and explanatory diagrams of essential parts of a memory device for explaining an example of a magnetic bubble memory device according to the present invention, in which the bias magnetic field HB and rotating magnetic field HR explained in FIG. 1 are generated. It is a diagram showing a circuit.

In these figures, 1 is a magnetic bubble memory chip.

2 is a permanent magnet that generates a bias magnetic field HB, and 3 is a magnetization plate that makes the bias magnetic field HB uniform.

A DC magnetic field H2 perpendicular to the magnetic field shunt plate 3 is created by the permanent magnet 2 and the magnetic field shunt plate 3.

In addition, 4 and 5 are an X coil and a Y coil that generate a rotating magnetic field HR, and by passing currents that are 90 degrees different in phase from each other through the X coil 4 and Y coil 5, A rotating magnetic field HR is obtained which rotates at .

6 is a spacer for inclining the xy plane of the chip 1 by an angle σ with respect to the Hz direction of the DC magnetic field.

In this case, the reason why the xy plane of the chip 1 is inclined by an angle σ with respect to the DC magnetic field Hz is that due to the inclination of the angle σ as illustrated in FIG. 5, the DC magnetic field Hz has a component Hh in the xy plane. It turns out.

Then, the magnitude of this in-plane component Hh is Hh sin
σ, usually Hz sin a=30e~60e
The inclination angle σ is selected so that

Further, the direction of this in-plane component Hh is inclined so as to coincide with the start/stop direction (+x-axis direction) of the rotating magnetic field HR.

This xy-plane component Hh is a known magnetic field called a holding field, which functions effectively for the start and stop operations of the rotating magnetic field HR.

Note that the magnitude of the bias magnetic field HB acting perpendicularly to the surface of the chip is Hz cosσ.

Now, since the above-mentioned holding field Hh is always acting on the plane xy of the chip 1, the rotating magnetic field H' acting on the chip 1 as illustrated in FIG.
R is eccentric.

In the figure, HR is a rotating magnetic field applied from the outside,
H'□ is a rotating magnetic field acting on the chip 1.

In this case, the rotating magnetic field HR1 acting on the chip 1 is a combination of the rotating magnetic field HR applied from the outside and the in-plane component Hh, and the center 6' of the rotating magnetic field HR1 is in the +X-axis direction, which is the start/stop direction. It moves by an in-plane component Hh.

For this reason, as illustrated in FIG. 6, for example, the rotating magnetic field H
270 degree phase at R and rotating magnetic field H' acting on chip 1
A difference of Aθ is generated between the phase of 270 degrees at R and the phase of 270 degrees.

The size of this Aθ is 270 degrees, becomes.

Here, IH,l represents the strength of the rotating magnetic field. In the case of 270 degrees as shown in the figure, this Aθ is a phase lead with respect to the chip 1.

FIG. 7 shows the results of determining the value of the phase shift Aθ at a phase of 270 degrees with respect to the size of various holding fields Hh.

In the same figure, the rotating magnetic field strength HR is 406e and 500e.
Two cases with e are shown.

Here, the value of the phase shift Jθ at the phase of 270 degrees varies due to the following three main factors in the magnetic bubble memory device shown in FIG. 4a.

That is, (1) the inclination angle σ of the xy plane of the chip 1 has a visibility variation of ±1 degree depending on the mounted circuit.

This is converted to holding field Hh by ±1.
50e~±2. It will be about OOe.

(2) The rotating magnetic field intensities IH and I vary by about ±10φ due to variations in the coil current due to variations in the power supply voltage.

For example, even if 1HR1 is set to about 456e, it actually varies within the range of 400e to 500e.

(3) The imbalance between the positive amplitude and negative amplitude of the coil current is approximately ±5φ.

Therefore, due to this imbalance, HR1450
In the case of e, the center of the rotating magnetic field HR is eccentric by about ±1.06e.

In other words, due to the above factors, the phase shift Jθ varies by approximately ±3 degrees from FIG. 7, due to factor (2), the phase shift varies by approximately ±1 degree from FIG. The phase shift varies by about ±1 degree.

Therefore, the fluctuation width All of the phase shift Aθ at the phase of 270 degrees described in FIG. 6 due to the variation in the mounted circuit is the sum of the fluctuations due to the above three main factors.

As a result of these various studies, we found that the cause of the variation in the lower limit value θ1 and upper limit value θ2 of the pulse phase θ, which halves the apparent phase margin JM'θ described in FIG. 3, is the fluctuation of this phase shift Aθ. It became clear that this was due to Al.

In the results shown in Figure 3, the variation between the lower limit value θ1 and the upper limit value θ2 is about ±4 degrees, and this value is the fluctuation range Jl of equation (1).
This can be well understood from the fact that it is in good agreement with

Therefore, in order to suppress the amount of decrease in the apparent phase margin AM'θ, it is sufficient to reduce Jl in equation (1).

To this end, it is sufficient to reduce the variations due to the three main factors mentioned above.

However, these variations are difficult to avoid in practice, and suppressing them to a small value would result in the creation of an expensive mounted circuit, which is not practical.

On the other hand, the median value θ of the phase margin JMθ of the operating pulse
If C is selected around a certain special value, even if 11 in equation (1) varies greatly, the lower limit value θ and upper limit value θ2 of the phase margin will have almost no variation, and the apparent phase margin JM We found that the amount of decrease in θ can be made close to zero.

This will be explained below.

FIG. 8 shows the results of the phase shift amount Jθ described in FIGS. 6 and 7 for various phases of the rotating magnetic fields HR and HR/.

(The results shown in FIG. 7 were for the case where the phase θ was 270 degrees.

) Also, the results in Figure 8 show that the rotating magnetic field strength HB ” 40
0e, holding field Hh = 4.00
This is the case of e.

As is clear from the results in the same figure, the rotating magnetic field HR2HR1
The phase shift amount Aθ is zero at points where the phase of is 0 degrees and 180 degrees.

Here, the point of phase θ = 0 degrees is the start point of the rotating magnetic field HR.
It is the stop (St/Sp) direction, and the point at phase θ2180 degrees is the start/stop (St/Sp) direction of the rotating magnetic field HR.
) is a point in the opposite direction.

On the other hand, at the phase θ perpendicular to the start/stop (St/Sp) direction, that is, at the points θ−90 degrees and θ=270 degrees, the phase shift amount Aθ is maximum.

Here, in the phase where the phase shift amount Aθ becomes zero, the fluctuation range 41 described in equation (1) also becomes zero.

This is based on the fact that the phase shift amount Aθ, which is the object of the variation width Al, is always zero with respect to the three main factors mentioned above, and as a result, the variation width Al of the phase shift amount Aθ is also zero.

Therefore, the median value θC of the phase margin JMθ of the operating pulse of the magnetic bubble memory chip is the phase shift amount Jθ=
phase θ, that is, the start/stop (St/Sp) direction or start/stop (S
t/Sp) direction, the amount of decrease in the apparent phase margin AM'θ can be suppressed to near zero.

In addition, as mentioned above, as a method of selecting the median value θC of the pulse phase margin JMθ, (4) Start/stop of the rotating magnetic field H□ (St/Sp
There were two cases: (B) when moving in the opposite direction to the start/stop (St/Sp) direction.

These two cases (4) added in Figure 8
, (B), case (4) has the following advantages.

In other words, in case (4), the lower limit value θ1 of the pulse phase
is within the phase advance region of the phase shift amount Aθ, and the upper limit value θ
2 is within the phase delay region of the phase shift amount Jθ.

Therefore, the effective phase margin JMθ is the upper limit value θ2~
It has the advantage of being wider than the lower limit θ1.

On the other hand, in case (B), the situation is reversed, and the effective phase margin becomes narrower from the upper limit value θ2 to the lower limit value θ.

Therefore, it is preferable to use case (4) for an operation pulse with a particularly narrow phase margin width JMθ.

In this case, the magnetic bubble memory chip in which the median value θC of the phase margin JMθ of the operating pulse is in the start-stop (St/Sp) direction or in the opposite direction to the start-stop (St/Sp) direction is This can be easily achieved by carefully designing the direction of the patterns in the chip.

Further, it is not necessary to set the median value θC of all the various operating pulse currents supplied to the chip as described above, and it may be carried out only for those with a narrow phase margin JMθ.

Further, in the above description, the case where the rotating magnetic field HR is circular has been explained, but the same effects as described above can be obtained even when the rotating magnetic field HR is rectangular, hexagonal, or other shapes.

As explained above, according to the magnetic bubble memory device of the present invention, the width of variation in the upper limit value and lower limit value of the pulse phase after the magnetic bubble memory chip is incorporated into the memory device is reduced, and the apparent pulse phase margin is An extremely excellent effect can be obtained in which the amount of decrease in is brought close to zero, and the phase margin width of the operating pulse in the stable operating region can be greatly expanded.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an operational configuration diagram of a magnetic bubble memory device. FIG. 2 is a diagram showing an example of the phase margin of the operating pulse current, FIG. 3 is a diagram showing an example of variation in the phase margin, and FIGS. 4a, b to 8 illustrate the magnetic bubble memory device according to the present invention. This is a diagram for 1...Magnetic bubble memory chip, 2...
・Permanent magnet, 3...magnetic shunt plate, 4...X
Coil, 5...Y coil, 6...Spacer.

Claims (1)

[Claims] 1. A magnetic bubble memory chip, a rotating magnetic field generating circuit that applies a horizontal rotating magnetic field to the magnetic bubble memory chip,
A magnetic bubble memory comprising: a bias magnetic field generation circuit that applies a direct current magnetic field perpendicular to the magnetic bubble memory chip; and an operation pulse current generation circuit that supplies operation pulses that cause the magnetic bubble memory chip to generate, transfer, and divide magnetic bubbles. 1. A magnetic bubble memory device, wherein a median value of a phase margin of at least some of the operating pulses is set to a value near a start/stop direction of the rotating magnetic field or a direction opposite thereto. 2. The magnetic bubble memory according to claim 1, wherein the median value of the operation pulse having a narrow pulse phase margin width is set to a value near the start/stop direction of the rotating magnetic field. Device.