Abstract:
A memory structure and data writing method thereof includes a power supply circuit and a bridge circuit. The bridge circuit is driven by the power supply circuit, and operate in a plurality of conduction modes. The memory structure only requires one set of power supply circuit and does not need to know the resistance of the bit line in advance, also the signal error is hardly occurred when the memory structure is switching between positive and negative.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to memory structures and data writing method thereof, and, more particularly, to a memory structure and a data writing method for a magnetic random access memory. 
       BACKGROUND OF THE INVENTION 
       [0002]    The data writing method of MRAM is to use two wirings (Bit Line and Write World Line) to induce the cell interconnected by the magnetic field, in order to change the magnetoresistance value of the memory layer by changing the direction of the magnetization state of the magnetic material of the memory layer. Thus, when reading the memory information, uses the reading of the resistance value generated by flowing the current into the selected magnetic memory cell to judge the bit value of the memory information. 
         [0003]    Referring to TW Patent No. 583666, it discloses a method to switch a magnetoresistive memory device by providing a magnetoresistive memory element close to a first conductor and a second conductor, wherein the magnetoresistive memory element includes a first magnetic region and a second magnetic region, and these two regions are divided by a tunneling barrier. At least one of the first and second magnetic regions comprises N ferromagnetic material layers that are antiferromagnetically coupled. N is an integral number equal or greater than two, and every single layer has an adjusted magnetic moment to provide a data writing mode. Every first and second magnetic region has a magnetic moment vector close to the tunneling barrier: at time t 0 , it is oriented in a preferable direction; at time t 1 , it is connected to a first current flowing through the first conductor; at time t 2 , it is connected to a second current flowing through the second conductor; at time t 3 , it cuts the first current flowing through the first conductor; at time t 4 , it cuts the second current flowing through the second conductor and this makes the magnetic moment closing to the tunneling barrier positioned in a direction different to the initial preferable direction at time t 0 . 
         [0004]    Conventional magnetoresistive memory device uses toggle mode to increase the data writing selectivity, in order to push the magnetoresistive memory close to the mass production stage. Referring to  FIGS. 14A ,  14 B,  14 C,  14 E and  14 E, they are the schematic views showing the time sequence and the data writing mode of the conventional magnetoresistive memory device according to the embodiment. The magnetoresistive memory applies a word current  30  and a bit current  40  to the magnetic field to cause a throughput of the magnetic field to rotate the effective magnetic moment vector of the magnetoresistive memory device 180 degree. However, because of the disturbance from the exposed magnetic field, the initial direction of the magnetoresistive memory device at time t 0  is often being deflected and sometimes causing data writing error. Therefore, the magnetoresistive memory device disclosed from the patent mentioned above uses a negative current to flow through before data writing, in order to deflect the magnetoresistive memory back to the correct initial direction at time t 0  to resolve the disturbance from the exposed magnetic field, and hence increases the ratio of the correct data writing. 
         [0005]    Although the magnetoresistive memory has advantages of non-volatility, high density, fast read/write and high endurance, but because of the especial toggle mode, a larger data writing magnetic field is required. Therefore, it is easy to cause a larger data writing current and increases the difficulty to match with other peripheral devices. However, although the switching method for the magnetoresistive memory mentioned above can reduce the data writing current and increase the magnetoresistive memory&#39;s correct data writing rate, but how to generate the forward and backward current mentioned in this method has become a problem for the related researchers. 
         [0006]    Therefore, how to develop a memory structure with a simple structure, a fixed current, and is able to generate the forward and backward current has become an urgent problem for the related researching field. 
       SUMMARY OF THE INVENTION 
       [0007]    In light of the above drawbacks in the prior art, an objective of the present invention is to provide a memory structure and data writing method thereof that is simple in structure and only requires one set power supply circuit. 
         [0008]    Another objective of the present invention is to provide a memory structure and data writing method thereof that is able to provide a positive pulse and a negative pulse. 
         [0009]    A further objective of the present invention is to provide a memory structure and data writing method thereof that can apply the current form the power supply circuit straight without knowing the resistance of the bit line in advance. 
         [0010]    In accordance with the above and other objectives, the present invention of a memory structure and data writing method thereof includes a power supply circuit with an input terminal and an output terminal, and a bridge circuit electrically connected to the power supply circuit having a first switch, a second switch, a third switch and a fourth switch to form a two-phase circuit. 
         [0011]    The memory structure of the present invention is applying the power supply circuit to drive the bridge circuit to generate a plurality of conduction modes that include: when the first and third switches are conductive (close), and the second and fourth switches are not conductive (open), the current flows from the input terminal to the resistance component via the first switch to generate a first pulse, then flows to the output terminal via the third switch; when the second and fourth switches are in conduction, and the first and third switches are in non-conduction, the current flows from the input terminal to the resistance component via the second switch to generate a second pulse, then flows to the output terminal via the fourth switch; and when the first, second, third and fourth switches are all in non-conduction, the current from the input terminal does not flow through any switches, hence generates a third pulse. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic structure view showing a memory structure of the present invention; 
           [0013]      FIGS. 2A ,  2 B and  2 C are schematic structure views showing different conduction mode of the memory structure of the present invention; 
           [0014]      FIG. 3  is a graph showing the waveform in conduction of the memory structure of the present invention; 
           [0015]      FIG. 4A  is a schematic structure view of the memory structure according to the first embodiment of the present invention; 
           [0016]      FIG. 4B  is a graph showing the simulated waveform of the memory structure according to the first embodiment of the present invention; 
           [0017]      FIG. 5A  is a schematic structure view of the memory structure according to the second embodiment of the present invention; 
           [0018]      FIG. 5B  is a graph showing the simulated waveform of the memory structure according to the second embodiment of the present invention; 
           [0019]      FIG. 6A  is a schematic structure view of the memory structure according to the third embodiment of the present invention; 
           [0020]      FIG. 6B  is a graph showing the simulated waveform of the memory structure according to the third embodiment of the present invention; 
           [0021]      FIG. 7A  is a schematic structure view of the memory structure according to the fourth embodiment of the present invention; 
           [0022]      FIG. 7B  is a graph showing the simulated waveform of the memory structure according to the fourth embodiment of the present invention; 
           [0023]      FIG. 8A  is a schematic structure view of the memory structure according to the fifth embodiment of the present invention; 
           [0024]      FIG. 8B  is a graph showing the simulated waveform of the memory structure according to the fifth embodiment of the present invention; 
           [0025]      FIG. 9A  is a schematic structure view of the memory structure according to the sixth embodiment of the present invention; 
           [0026]      FIG. 9B  is a graph showing the simulated waveform of the memory structure according to the sixth embodiment of the present invention; 
           [0027]      FIG. 10A  is a schematic structure view of the memory structure according to the seventh embodiment of the present invention; 
           [0028]      FIG. 10B  is a graph showing the simulated waveform of the memory structure according to the seventh embodiment of the present invention; 
           [0029]      FIG. 11A  is a schematic structure view of the memory structure according to the eighth embodiment of the present invention; 
           [0030]      FIG. 11B  is a graph showing the simulated waveform of the memory structure according to the eighth embodiment of the present invention; 
           [0031]      FIG. 12A  is a schematic structure view of the memory structure according to the ninth embodiment of the present invention; 
           [0032]      FIG. 12B  is a graph showing the simulated waveform of the memory structure according to the ninth embodiment of the present invention; 
           [0033]      FIG. 13A  is a schematic structure view of the memory structure according to the tenth embodiment of the present invention; 
           [0034]      FIG. 13B  is a graph showing the simulated waveform of the memory structure according to the tenth embodiment of the present invention; 
           [0035]      FIG. 14A  is a schematic view showing the time sequence of the conventional magnetoresistive memory device according to the embodiment; and 
           [0036]      FIGS. 14B ,  14 C,  14 C,  14 D and  14 E are schematic views showing the data writing mode of the conventional magnetoresistive memory device according to the embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparently understood by those in the art after reading the disclosure of this specification. The present invention can also be performed or applied by other different embodiments. The details of the specification may be on the basis of different points and applications, and numerous modifications and variations can be devised without departing from the spirit of the present invention. 
         [0038]      FIG. 1  is a circuit diagram of a memory structure of the present invention. The memory structure of the present invention comprises a power supply circuit  10  and a bridge circuit  20 . The bridge circuit  20  is driven by the power supply circuit  10 , and operates in a plurality of conduction modes. The power supply circuit  10  comprises an input terminal  11  and an output terminal  12 . The bridge circuit  12  comprises a first switch  21 , a second switch  22 , a third switch  23  and a fourth switch  24 , all of which are used for forming a two-phase circuit. Two opposite junctions of the bridge circuit  20  are connected to the input terminal  11  and the output terminal  12  respectively, and another two opposite junctions of the bridge circuit  20  serve as conduction paths for currents. 
         [0039]    The first switch  21 , second switch  22 , third switch  23  and fourth switch  24  of the bridge circuit  20  mentioned above can be assembled from the group consisting of P-channel field effect transistor (FET) and N-channel FET, or a transmission gate assembled by P-channel FET and N-channel FET, or P-channel FET, N-channel FET and transmission gate. For example, the bridge circuit  20  can be composed of two P-channel FETs and two N-channel FETs. The P-channel and N-channel FETs forms a positive half-cycled drive and a negative half-cycled drive. The bridge circuit  20  further comprises a resistance component  25  (also called bit line) connected to the another two junctions of the bridge circuit  20 . The resistance component  25  comprises a resistance of a bit line  251 . 
         [0040]      FIGS. 2A ,  2 B,  2 C and  3  are four views showing the structure under different conduction modes and the conduction waveform of the memory structure of the present invention. The bridge circuit  20  is driven by currents generated by the power supply circuit  10  to operate in the connection modes. 
         [0041]    As shown in  FIG. 2A , when the first and third switches  21 ,  23  are conductive, and the second and fourth switches  22 ,  24  are not conductive, currents  26  travels from the input terminal  11  of the power supply circuit  10  to the resistance component  25  via the first switch  21 . The resistance component  25  generates currents flowing downward. The downward-flowing currents are called first pulses  261 . The first pulses  261 , also known as positive pulse, then flow to the output terminal  12  of the power supply circuit  10  via the third switch  23 . 
         [0042]    As shown in  FIG. 2B , when the second and fourth switches  22 ,  24  are conductive, and the first and third switches  21 ,  23  are not conductive, the currents  26  flow from the input terminal  11  of the power supply circuit  10  to the resistance component  25  via the second switch  22 . The resistance component  25  generates another currents flowing upward. The upward-flowing currents are also called second pulses  262 . The second pulses  262 , also known as negative pulse, then flow to the output terminal  12  of the power supply circuit  10  via the fourth switch  24 . 
         [0043]    As shown in  FIG. 2C , when the first, second, third and fourth switches  21 ,  22 ,  23 ,  24  are all not conductive, the currents  26  flew from the input terminal  11  of the power supply circuit  10  do not flow through any bit line (the resistance component  25 ). Therefore, third pulses  263  are generated. The third pulses  263  are known as common pulses. 
         [0044]    Besides, the memory structure of the present invention can be altered according to the reality needs.  FIGS. 4A ,  4 B,  5 A,  5 B,  6 A and  6 B are six views showing the structure and the conduction waveform of the memory structure according to different embodiments of the present invention. 
         [0045]      FIGS. 4A and 4B  are two schematic diagrams showing the structure and the simulated waveform of the memory structure according to a first embodiment of the present invention. The switch is assembled by transmission gate that is consisted of P-channel FET and N-channel FET. The first switch  21 , third switch  23 , second switch  22  and fourth switch  24  of the full bridge circuit share a first control signal (V_Ctrl_B)  13  and a second control signal (V_Ctrl)  14 . Thus, when the memory structure switches between positive and negative, the full bridge circuit uses the first and second control signal  13 ,  14  respectively, leads to that the first and second control signal  13 ,  14  can be adjusted separately to avoid the error occurred therein. That means the full bridge circuit will not be in conduction for all switches at the same time, and hence the possibility of occurring signal errors is reduced. 
         [0046]      FIGS. 5A and 5B  are two schematic diagrams showing the structure and the simulated waveform of the memory structure according to the second embodiment of the present invention. The first and fourth switches  21 ,  24  of the full bridge circuit are N-channel FETs, and the second and third switches  22 ,  23  of the full bridge circuit are P-channel FETs. Through the different characteristics of the P-channel FET and N-channel FET, positive and negative pulses with different magnitude are generated. 
         [0047]      FIGS. 6A and 6B  are two schematic diagrams showing the structure and the simulated waveform of the memory structure according to the third embodiment of the present invention. The present embodiment is most similar to the previous second embodiment, the only difference is that at the present embodiment, the first and fourth switches  21 ,  24  of the full bridge circuit are P-channel FETs and the second and third switches  22 ,  23  of the full bridge circuit are N-channel FETs. Through the different characteristics of the FETs mentioned above, positive and negative pulses with different magnitude are generated. 
         [0048]    As shown in  FIGS. 7A and 7B , they are schematic diagrams showing the structure and the simulated waveform of the memory structure according to the fourth embodiment of the present invention. The first and second switches  21 ,  22  of the full bridge circuit are P-channel FETs and the third and fourth switches  23 ,  24  of the full bridge circuit are N-channel FETs. Also the first and fourth switches  21 ,  24  share an externally connected first control signal  13  and the second and third switches  22 ,  23  share a second control signal  14  in order to produce a time-lagging, and symmetrical positive and negative pulses are generated. 
         [0049]    As shown in  FIGS. 8A and 8B , they are schematic diagrams showing the structure and the simulated waveform of the memory structure according to the fifth embodiment of the present invention. The present embodiment is most similar to the previous first embodiment, the only difference is that at the present embodiment, the first and third switches  21 ,  23  of the full bridge circuit is a transmission gate consisted of P-channel FET and N-channel FET, and the second and fourth switches  22 ,  24  of the full bridge circuit are P-channel FETs. Through the different characteristics of the FETs mentioned above, positive and negative pulses with different magnitude are generated. 
         [0050]    As shown in  FIGS. 9A and 9B , they are schematic diagrams showing the structure and the simulated waveform of the memory structure according to the sixth embodiment of the present invention. The present embodiment is most similar to the previous first embodiment, the only difference is that at the present embodiment, the second and third switches  22 ,  23  of the full bridge circuit is a transmission gate and the first and fourth switches  21 ,  24  of the full bridge circuit are P-channel FETs. Through the different characteristics of the FETs mentioned above, positive and negative pulses with different magnitude are generated. 
         [0051]    As shown in  FIGS. 10A and 10B , they are schematic diagrams showing the structure and the simulated waveform of the memory structure according to the seventh embodiment of the present invention. The present embodiment is most similar to the previous first embodiment, the only difference is that at the present embodiment, the third and fourth switches  23 ,  24  of the full bridge circuit is a transmission gate, the first switch  21  of the full bridge circuit is P-channel FET and the second switch  22  of the full bridge circuit is N-channel FET. Through the different characteristics of the FETs mentioned above, positive and negative pulses with different magnitude are generated. 
         [0052]    As shown in  FIGS. 11A and 11B , they are schematic diagrams showing the structure and the simulated waveform of the memory structure according to the eighth embodiment of the present invention. The present embodiment is most similar to the previous first embodiment, the only difference is that at the present embodiment, the first and second switches  21 ,  22  of the full bridge circuit is a transmission gate, the third switch  23  of the full bridge circuit is N-channel FET and the fourth switch  24  of the full bridge circuit is P-channel FET. Through the different characteristics of the FETs mentioned above, positive and negative pulses with different magnitude are generated. 
         [0053]    As shown in  FIGS. 12A and 12B , they are schematic diagrams showing the structure and the simulated waveform of the memory structure according to the ninth embodiment of the present invention. The present embodiment is most similar to the previous first embodiment, the only difference is that at the present embodiment, the third and fourth switches  23 ,  24  of the full bridge circuit is a transmission gate and the first and second switches  21 ,  22  of the full bridge circuit are P-channel FETs. Through the different characteristics of the FETs mentioned above, symmetrical positive and negative pulses are generated. 
         [0054]    As shown in  FIGS. 13A and 13B , they are schematic diagrams showing the structure and the simulated waveform of the memory structure according to the tenth embodiment of the present invention. The present embodiment is most similar to the previous first embodiment, the only difference is that at the present embodiment, the first and second switches  21 ,  22  of the full bridge circuit is a transmission gate and the third and fourth switches  23 ,  24  of the full bridge circuit are N-channel FETs. Through the different characteristics of the FETs mentioned above, symmetrical positive and negative pulses are generated. 
         [0055]    In conclude with the description stated above, the memory structure of the present invention comprises a power supply circuit and a bridge circuit. Through the driving of the power supply circuit to let the bridge circuit switches between forward and backward, positive pulse, negative pulse and common pulse are generated. The memory structure is simple in configuration and only needs one set of power supply circuit, which means the current form the power supply circuit can be applied straight without knowing the resistance of the bit line in advance, hence this memory structure is easy to match with other peripheral equipment. 
         [0056]    Moreover, the memory structure of the present invention can be altered according to different needs in reality. The memory structure can share or externally connect to different control signal respectively, and through the different characteristic of the P-channel FET and N-channel FET, the signal error is hardly occurred for the memory structure when switching between forward and backward. Also the forward and backward switch can be adjusted, thus the amount of the forward and backward current can be changed. 
         [0057]    The present invention has been described using exemplary preferred embodiments above, however, it is to be understood that the scope of the present invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar changes. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.