Thin film magnetic memory device with memory cell having magnetic tunnel junction
View Patent ↗In this MRAM device, a memory block is divided into 4 regions, and 4 constant current circuits are respectively provided corresponding to the 4 regions. Bit line drivers select 2 bit lines from each of the 4 regions, that is, 8 bit lines are selected. Bit line drivers supply, to each bit line, an output current from the constant current circuit corresponding to that bit line. Accordingly, a write current flowing through a bit line can be stabilized, and stable data writing can be achieved.
1. A thin film magnetic memory device comprising:
a plurality of memory cells, each magnetically storing a data signal;
a plurality of data write lines respectively provided corresponding to said plurality of memory cells;
a constant current circuit outputting a prescribed constant current;
a write circuit selecting any of said plurality of memory cells in accordance with an address signal, supplying an output current from said constant current circuit to the data write line corresponding to the selected memory cell, and writing a data signal to the memory cell;
a spare memory cell for replacing a defective memory cell in said plurality of memory cells; and
a spare data write line provided corresponding to said spare memory cell; wherein
said write circuit selects said spare memory cell instead of said defective memory cell when said defective memory cell is designated by said address signal, and supplies the output current from said constant current circuit to said spare data write line and writes a data signal to said spare memory cell.
2. A thin film magnetic memory device, comprising:
a plurality of memory cells, each magnetically storing a data signal;
a plurality of data write lines respectively provided corresponding to said plurality of memory cells;
a constant current circuit outputting a prescribed constant current; and
a write circuit selecting any of said plurality of memory cells in accordance with an address signal, supplying an output current from said constant current circuit to the data write line corresponding to the selected memory cell, and writing a data signal to the memory cell, wherein
said plurality of memory cells are grouped together in Ns (N=an integer equal to 2 or larger) in advance, and
said write circuit selects any of a plurality of memory cell groups in accordance with said address signal, divides the output current from said constant current circuit to N data write lines corresponding to the selected memory cell group, and writes a data signal to each of N memory cells belonging to the memory cell group.
3. The thin film magnetic memory device according to claim 2 , further comprising:
N spare memory cells for replacing N memory cells belonging to a defective memory cell group in said plurality of memory cell groups; and
N spare data write lines respectively provided corresponding to said N spare memory cells; wherein
said write circuit selects said N spare memory cells instead of said defective memory cell group when said defective memory cell group is designated by said address signal, divides the output current from said constant current circuit to said N spare data write lines, and writes a data signal to each of said N spare memory cells.
4. A thin film magnetic memory device, comprising:
a plurality of memory cells, each magnetically storing a data signal;
a plurality of data write lines respectively provided corresponding to said plurality of memory cells;
a constant current circuit outputting a prescribed constant current; and
a write circuit selecting any of said plurality of memory cells in accordance with an address signal, supplying an output current from said constant current circuit to the data write line corresponding to the selected memory cell, and writing a data signal to the memory cell, wherein
said plurality of memory cells are arranged in a plurality of rows and a plurality of columns, and
said plurality of data write lines include a plurality of bit lines respectively provided corresponding to said plurality of columns,
said thin film magnetic memory device further comprising a plurality of digit lines respectively provided corresponding to said plurality of rows, wherein
said write circuit includes
a digit line driver selecting any of said plurality of digit lines in accordance with a row address signal and supplying a write current to the selected digit line, and
a bit line driver selecting any of said plurality of bit lines in accordance with a column address signal and supplying the output current from said constant current circuit to the selected bit line.
5. A thin film magnetic memory device, comprising:
a plurality of memory cells, each magnetically storing a data signal;
a plurality of data write lines respectively provided corresponding to said plurality of memory cells;
a constant current circuit outputting a prescribed constant current; and
a write circuit selecting any of said plurality of memory cells in accordance with an address signal, supplying an output current from said constant current circuit to the data write line corresponding to the selected memory cell, and writing a data signal to the memory cell, wherein
said plurality of memory cells are arranged in a plurality of rows and a plurality of columns, and
said plurality of data write lines include a plurality of digit lines respectively provided corresponding to said plurality of rows,
said thin film magnetic memory device further comprising a plurality of bit lines respectively provided corresponding to said plurality of columns, wherein
said write circuit includes
a digit line driver selecting any of said plurality of digit lines in accordance with a row address signal and supplying the output current from said constant current circuit to the selected digit line, and
a bit line driver selecting any of said plurality of bit lines in accordance with a column address signal and supplying a write current to the selected bit line.
6. A thin film magnetic memory device, comprising:
a plurality of memory cells, each magnetically storing a data signal;
a plurality of data write lines respectively provided corresponding to said plurality of memory cells;
a constant current circuit outputting a prescribed constant current; and
a write circuit selecting any of said plurality of memory cells in accordance with an address signal, supplying an output current from said constant current circuit to the data write line corresponding to the selected memory cell, and writing a data signal to the memory cell, wherein
said constant current circuit includes
a first transistor connected between a line of a power supply potential and an output node, having an input electrode receiving a control voltage, and supplying said constant current, and
a second transistor connected between said output node and a line of a ground potential and rendered non-conductive upon output of said constant current.
7. The thin film magnetic memory device according to claim 6 , wherein
said second transistor supplies a current at a level approximately equal to a level of said constant current upon conduction of said second transistor.
8. The thin film magnetic memory device according to claim 6 , wherein
said second transistor is rendered non-conductive in response to said output node being coupled to said data write line by said write circuit.
9. A thin film magnetic memory device, comprising:
a plurality of memory cells, each magnetically storing a data signal;
a plurality of data write lines respectively provided corresponding to said plurality of memory cells;
a constant current circuit outputting a prescribed constant current; and
a write circuit selecting any of said plurality of memory cells in accordance with an address signal, supplying an output current from said constant current circuit to the data write line corresponding to the selected memory cell, and writing a data signal to the memory cell, wherein
a current necessary to be supplied to said data write line to write a data signal to said memory cell varies in accordance with a certain parameter,
said constant current circuit alters a level of said constant current in accordance with said certain parameter, and
said certain parameter includes a temperature.
10. The thin film magnetic memory device according to claim 9 , wherein
said constant current circuit includes
a proportional to absolute temperature current generation circuit outputting a current proportional to an absolute temperature,
a temperature dependence current generation circuit outputting a current having a temperature dependence different from a temperature dependence of an output current from said proportional to absolute temperature current generation circuit, and
a constant current generation circuit outputting said constant current depending on the output current from said proportional to absolute temperature current generation circuit and an output current from said temperature dependence current generation circuit.