Memory array with power-efficient read architecture

1. An apparatus, comprising:

a first string of memory cells; and

a second string of memory cells, the second string of memory cells being configured to receive at least a portion of a current flowing in the first string of memory cells during a read operation, the first string of memory cells and the second string of memory cells being coupled by a common node located therebetween.

2. The apparatus of claim 1 , wherein the common node comprises a common source that is configured to be electrically coupled to at least one of the first string of memory cells and the second string of memory cells.

3. The apparatus of claim 2 , wherein the common source is selected to be one source from a group including a source line, a source slot, and a source diffusion region.

4. The apparatus of claim 1 , wherein the first string of memory cells and the second string of memory cells are each coupled to a separate sense circuit.

5. The apparatus of claim 1 , further comprising a select device to electrically couple the second string to the first string through the common node during the read operation.

6. The apparatus of claim 1 , further comprising:

a first select transistor coupled to the first string of memory cells;

a first current source;

a first data line coupled to the first select transistor and the first current source, the first select transistor being configured to selectively couple current provided by the first current source to the first string of memory cells;

a second select transistor coupled to the second string of memory cells;

a second current source; and

a second data line coupled to the second select transistor and the second current source, the second select transistor being configured to selectively couple current provided by the second current source to the second string of memory cells.

7. An apparatus, comprising:

a first string of memory cells coupled to a first current source at a first end and to a common node at a second end through a first select transistor; and

a second string of memory cells coupled to a second current source at a first end and to the common node at a second end through a second select transistor,

wherein the second string of memory cells is configured to receive at least a portion of a current flowing in the first string of memory cells during a read operation.

8. The apparatus of claim 7 , further comprising a first sense circuit and a second sense circuit to couple to the first string of memory cells and the second string of memory cells, respectively.

9. The apparatus of claim 7 , wherein the first current source comprises a first power enable element coupled to the first data line and wherein the second current source comprises a second power enable element coupled to the second data line.

10. The apparatus of claim 9 , wherein the first power enable element and the second power enable element are configured to be activated by bias voltages of opposite polarities.

11. A three-dimensional memory apparatus having various levels of memory, the apparatus comprising:

an upper-memory element having at least a first memory string and a second memory string;

a lower-memory element having at least a third memory string and a fourth memory string;

a common node formed between the upper-memory element and the lower-memory element; and a separate current source coupled to each of the memory strings,

wherein the lower-memory element is configured to receive at least a portion of a current flowing in the upper-memory element during a read operation.

12. The three-dimensional memory apparatus of claim 11 , further comprising:

the first memory string and the second memory string being formed substantially parallel and adjacent to one another; and

the third memory string and the fourth memory string being formed substantially parallel and adjacent to one another.

13. The three-dimensional memory apparatus of claim 11 , further comprising a separate sense circuit coupled to each of the memory strings.

14. The three-dimensional memory apparatus of claim 11 , further comprising:

a first select transistor and a third select transistor configured to electrically couple the first memory string and the third memory string, respectively, to each other in series and to the common node, the common node being located between the first select transistor and the third select transistor; and

a second select transistor and a fourth select transistor to electrically couple the second memory string and the fourth memory string, respectively, to each other in series and to the common node, the common node being located between the second select transistor and the fourth select transistor.

15. The three-dimensional memory apparatus of claim 11 , wherein the first memory string and the third memory string are configured to be coupled to each other in series, and the second memory string and the fourth memory string are configured to be coupled to each other in series, during a concurrent read operation of the first, second, third, and fourth memory strings.

16. The three-dimensional memory apparatus of claim 15 , wherein the first memory string and the second memory string are configured to be read concurrently.

17. A method of reading memory cells, the method comprising:

activating a first select transistor and a second select transistor to couple a first string of memory cells and a second string of memory cells in series;

coupling a first sense circuit and a second sense circuit to the first string of memory cells and the second first string of memory cells, respectively; and

providing a read current through the first string of memory cells and through the second string of memory cells substantially concurrently.

18. The method of claim 17 , further comprising receiving in the second string of memory cells at least a portion of a current flowing in the first string of memory cells during a read operation.

19. The method of claim 17 further comprising reading the first string of memory cells and the second string of memory cells concurrently.