1. A memory device comprising:
a plurality of magnetic random access memory (MRAM) cells that are electrically connected in series to allow the flow of a common current through each one of the MRAM cells, each one of the MRAM cells having a storage magnetization direction and a sense magnetization direction,
wherein, during a write operation, multiple ones of the MRAM cells are configured to be written in parallel by switching the storage magnetization directions of the MRAM cells, and wherein, during a read operation, a particular one of the MRAM cells is configured to be read by varying the sense magnetization direction of the particular one of the MRAM cells, relative to the storage magnetization direction of the particular one of the MRAM cells, and
wherein the multiple ones of the MRAM cells are configured to be heated by the common current in preparation for the write operation.
2. The memory device of claim 1, wherein the MRAM cells are arranged in a vertical stack.
3. The memory device of claim 1, wherein the MRAM cells are arranged in a horizontal array.
4. The memory device of claim 1, wherein the storage magnetization direction of each one of the MRAM cells is switchable between a plurality of directions to store at least a portion of a multi-bit data value.
5. The memory device of claim 4, wherein, during the write operation, the multi-bit data value is written into the MRAM cells, with each one of the MRAM cells storing a respective portion of the multi-bit data value.
6. The memory device of claim 5, wherein, during the read operation, the sense magnetization direction of the particular one of the MRAM cells being read is varied to determine the portion of the multi-bit data value stored by the particular one of the MRAM cells.
7. The memory device of claim 1, wherein at least one of the MRAM cells includes:
a sense layer having a sense magnetization direction;
a storage layer having a storage magnetization direction;
a spacer layer disposed between the sense layer and the storage layer; and
a pinning layer disposed adjacent to the storage layer for stabilizing the storage magnetization direction with respect to a threshold temperature.
8. The memory device of claim 7, wherein the sense layer includes a first ferromagnetic material, the storage layer includes a second ferromagnetic material, and a coercivity of the first ferromagnetic material is smaller than a coercivity of the second ferromagnetic material.
9. The memory device of claim 1, further comprising a transistor electrically connected in series to the MRAM cells, and wherein the transistor is switchable to allow flow of a current through the MRAM cells.
10. The memory device of claim 1, wherein, during the read operation, the sense magnetization direction of the particular one of the MRAM cells being read is varied to determine a minimum of the resistance.
11. The memory device of claim 1, further comprising a plurality of field lines that are magnetically connected to respective ones of the MRAM cells, and wherein, during the write operation, each one of the field lines is configured to apply a write current to induce a write magnetic field.
12. The memory device of claim 11, wherein, during the read operation, a particular one of the field lines is selectively activated to apply a read current to induce a read magnetic field, and the sense magnetization direction of the particular one of the MRAM cells being read is varied in accordance with the read magnetic field.
13. The memory device of claim 1, wherein the MRAM cells are arranged in a first vertical stack, and the memory device further comprises a second vertical stack disposed adjacent to the first vertical stack.
14. The memory device of claim 1, wherein the multiple ones of the MRAM cells are configured to allow a common sense current to flow through the multiple ones of the MRAM cells.
15. The memory device of claim 1, wherein the multiple ones of the MRAM cells are configured to allow the flow of the common current in its entirety through each one of the multiple ones of the MRAM cells.
16. A method of operating a memory device, comprising:
providing a plurality of series-interconnected MRAM cells in the memory device so as to allow the flow of a common current through each one of the MRAM cells;
during a write operation, switching a storage magnetization direction of each one of the MRAM cells from an initial logic state to another logic state to store a respective portion of a multi-bit data value by applying a common heating current through multiple ones of the MRAM cells; and
during a read operation, varying a sense magnetization direction of a selected one of the MRAM cells, relative to the storage magnetization direction of the selected one of the MRAM cells, to determine the portion of the multi-bit data value stored by the selected one of the MRAM cells.
17. The method of claim 16, further comprising, during the write operation, applying a heating current through the MRAM cells to facilitate switching the storage magnetization directions of the MRAM cells.
18. The method of claim 16, further comprising, during the read operation, inducing a read magnetic field adjacent to the selected one of the MRAM cells to vary the sense magnetization direction of the selected one of the MRAM cells.
19. The method of claim 18, further comprising, during the read operation, applying a sense current through the MRAM cells to determine a resistance value of the MRAM cells, with the resistance value being dependent upon a degree of alignment between the sense magnetization direction and the storage magnetization direction of the selected one of the MRAM cells.
20. The method of claim 19, wherein, during the read operation, the sense magnetization direction of the selected one of the MRAM cells is varied to determine a minimum resistance value.
21. The method of claim 16, further comprising, during a read operation, varying a sense magnetization direction of a selected one of the MRAM cells, relative to the storage magnetization direction of the selected one of the MRAM cells, to determine the portion of the multi-bit data value stored by the selected one of the MRAM cells by applying a common sense current through the multiple ones of the MRAM cells to determine a resistance of the MRAM cells.
22. The method of claim 16, wherein the providing the plurality of the series-interconnected MRAM cells in the memory device is so as to allow the flow of the common current in its entirety through each one of the MRAM cells.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A driver circuit for delivering a generally constant voltage and generally constant current to a load comprising a plurality of LED arrays, the driver circuit comprising:
a source of incoming AC power;
a rectifier connected to the source of incoming AC power, the rectifier producing a DC voltage;
a constant voltage driver for receiving the DC voltage from the rectifier, the constant voltage driver comprising:
a selectively activated switching element for receiving the DC voltage;
a controller for receiving the DC voltage, the controller configured to send a drive signal to the switching element to activate the switching element;
an output line providing a generally constant voltage; and
a plurality of constant current drivers each directly in communication with the output line of the constant voltage driver to receive the generally constant voltage, wherein each of the plurality of constant current drivers provides a substantially constant current to a corresponding one of the plurality of LED arrays.
2. The driver circuit of claim 1, further comprising a buck converter in communication with the switching element, wherein the buck converter receives the DC voltage if the switching element is activated.
3. The driver circuit of claim 2, wherein the buck converter includes a freewheeling diode, a primary winding, and a secondary winding.
4. The driver circuit of claim 3, wherein the secondary winding is part of a voltage regulator circuit.
5. The driver circuit of claim 3, wherein a voltage from the primary winding is stepped down by the secondary winding before the voltage is sent to a linear voltage regulator.
6. The driver circuit of claim 1, wherein the switching element is a high-side switching element.
7. The driver circuit of claim 1, wherein the constant voltage driver includes a floating ground.
8. The driver circuit of claim 1, wherein the constant voltage driver is grounded to earth.
9. The driver circuit of claim 1, wherein the load is driven using pulse width modulated (PWM) control or linear control.
10. The driver circuit of claim 1, wherein the plurality of constant current drivers each includes a current controller for providing a generally constant current to the load.
11. The driver circuit of claim 1, wherein the plurality of constant current drivers are each grounded to earth.
12. The driver circuit of claim 1, wherein the plurality of constant current drivers each includes a floating ground.
13. The driver circuit of claim 1, wherein the plurality of LED arrays are based on red, green, blue (RGB) color mixing, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another to produce a light output of a specified color.
14. The driver circuit of claim 1, wherein the plurality of LED arrays comprise white LEDs, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another in order to modify a color temperature of the white LEDs.
15. The driver circuit of claim 1, wherein the plurality of LED arrays comprise white LEDs, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another such that as the LED arrays are dimmed, a color temperature of the plurality of LED arrays is increased.
16. The driver circuit of claim 1, further comprising an electromagnetic interference (EMI) filter connected to the rectifier.
17. A driver circuit for delivering a generally constant voltage and generally constant current to a plurality of LED arrays, the driver circuit comprising:
a source of incoming AC power;
a rectifier connected to the incoming source of AC power, the rectifier producing a DC voltage;
a constant voltage driver for receiving the DC voltage from the rectifier, wherein the constant voltage driver includes a floating ground, the constant voltage driver comprising:
a selectively activated high-side switching element for receiving the DC voltage;
a controller for receiving the DC voltage, the controller configured to send a drive signal to the high-side switching element to activate the high-side switching element; and
an output line providing a generally constant voltage; and
plurality of constant current drivers each directly in communication with the output line of the constant voltage driver to receive the generally constant voltage, wherein each of the plurality of constant current drivers provides a substantially constant current to a corresponding one of the plurality of LED arrays.
18. The driver circuit of claim 17, further comprising a buck converter in communication with the high-side switching element, wherein the buck converter receives the DC voltage if the high-side switch is activated.
19. The driver circuit of claim 18, wherein the buck converter includes a freewheeling diode, a primary winding, and a secondary winding.
20. The driver circuit of claim 19, wherein the secondary winding is part of a voltage regulator circuit.
21. The driver circuit of claim 19, wherein a voltage from the primary winding is stepped down by the secondary winding before the voltage is sent to a linear voltage regulator.
22. The driver circuit of claim 17, wherein the plurality of constant current drivers each includes a current controller for providing a generally constant current to the load.
23. The driver circuit of claim 17, wherein the plurality of constant current drivers are each grounded to earth.
24. The driver circuit of claim 17, wherein the plurality of LED arrays are based on red, green, blue (RGB) color mixing, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another to produce a light output of a specified color.
25. The driver circuit of claim 17, wherein the plurality of LED arrays comprise white LEDs, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another in order to modify a color temperature of the white LEDs.
26. The driver circuit of claim 17, wherein the plurality of LED arrays comprise white LEDs, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another such that as the LED arrays are dimmed, a color temperature of the plurality of LED arrays is increased.
27. A driver circuit for delivering a generally constant voltage and generally constant current to a plurality of LED arrays, the driver circuit comprising:
a source of incoming AC power;
a rectifier connected to the incoming source of AC power, the rectifier producing a DC voltage;
a constant voltage driver for receiving the DC voltage from the rectifier, wherein the constant voltage driver is grounded to earth, the constant voltage driver comprising:
a selectively activated switching element for receiving the DC voltage;
a controller for receiving the DC voltage, the controller configured to send a drive signal to the switching element to activate the switching element; and
an output line providing a generally constant voltage; and
plurality of constant current drivers each directly in communication with the output line of the constant voltage driver to receive the generally constant voltage, wherein each of the plurality of constant current drivers provides a substantially constant current to a corresponding one of the plurality of LED arrays.
28. The driver circuit of claim 27, further comprising a buck converter in communication with the switching element, wherein the buck converter receives the DC voltage if the switch is activated.
29. The driver circuit of claim 28, wherein the buck converter includes a freewheeling diode, a primary winding, and a secondary winding.
30. The driver circuit of claim 29, wherein the secondary winding is part of a voltage regulator circuit.
31. The driver circuit of claim 29, wherein a voltage from the primary winding is stepped down by the secondary winding before the voltage is sent to a linear voltage regulator.
32. The driver circuit of claim 27, wherein the plurality of constant current drivers each includes a current controller for providing a generally constant current to the load.
33. The driver circuit of claim 27, wherein the plurality of constant current drivers each include a floating ground.
34. The driver circuit of claim 27, wherein the plurality of LED arrays are based on red, green, blue (RGB) color mixing, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another to produce a light output of a specified color.
35. The driver circuit of claim 27, wherein the plurality of LED arrays comprise white LEDs, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another in order to modify a color temperature of the white LEDs.
36. The driver circuit of claim 27, wherein the plurality of LED arrays comprise white LEDs, and wherein each of the plurality of constant current drivers drives each of the plurality of LED arrays separately from one another such that as the LED arrays are dimmed, a color temperature of the plurality of LED arrays is increased.
37. A driver circuit for delivering a generally constant voltage and generally constant current to a load, the driver circuit comprising:
a source of incoming AC power;
a rectifier connected to the source of incoming AC power, the rectifier producing a DC voltage;
a constant voltage driver for receiving the DC voltage from the rectifier, the constant voltage driver comprising:
a selectively activated switching element for receiving the DC voltage;
a controller for receiving the DC voltage, the controller configured to send a drive signal to the switching element to activate the switching element;
an output line providing a generally constant voltage;
at least one constant current driver in communication with the output line of the constant voltage driver to receive the generally constant voltage; and
a buck converter in communication with the switching element, wherein the buck converter receives the DC voltage if the switching element is activated.
38. The driver circuit of claim 37, wherein the buck converter includes a freewheeling diode, a primary winding, and a secondary winding.
39. The driver circuit of claim 38, wherein the secondary winding is part of a voltage regulator circuit.
40. The driver circuit of claim 38, wherein a voltage from the primary winding is stepped down by the secondary winding before the voltage is sent to a linear voltage regulator.
41. The driver circuit of claim 37, wherein the switching element is a high-side switching element.
42. The driver circuit of claim 37, wherein the constant voltage driver includes a floating ground.
43. The driver circuit of claim 37, wherein the constant voltage driver is grounded to earth.