Thin film magnetic memory device with memory cells including a tunnel magnetic resistive element
View Patent ↗A data bus is precharged to a precharge voltage before data read operation. In the data read operation, the data bus thus precharged is electrically coupled to the same voltage as the precharge voltage through a selected memory cell. A driving transistor couples the data bus to a power supply voltage (driving voltage) in order to supply a sense current in the data read operation. A charge transfer amplifier portion produces an output voltage according to an integral value of the sense current (data read current) flowing through the data bus, while maintaining the data bus at the precharge voltage. A transfer gate, differential amplifier and latch circuit produce read data based on the output voltage sensed at prescribed timing.
1. A thin film magnetic memory device, comprising:
a plurality of magnetic memory cells for storing data written by an applied magnetic field;
a dummy memory cell for comparison with a selected one of said plurality of magnetic memory cells in data read operation, each of said magnetic memory cells and said dummy memory cell including
a magnetic storage portion having one of a first electric resistance value and a second electric resistance value that is larger than said first electric resistance value, according to a level of said storage data, and
a memory cell selection gate connected in series with said magnetic storage portion, and rendered conductive when selected, said magnetic storage portion included in said dummy memory cell storing data at a level corresponding to said first electric resistance value;
a first data line electrically coupled to one of said selected magnetic memory cell and said dummy memory cell in said data read operation;
a second data line electrically coupled to the other of said selected magnetic memory cell and said dummy memory cell in said data read operation;
a data read circuit for supplying a data read current to each of said first and second data lines and producing read data based on a voltage change on said first and second data lines in said data read operation; and
a dummy resistance adding circuit for selectively connecting a resistance portion in series with one of said first and second data lines that is electrically coupled to said dummy memory cell, said resistance portion having an electric resistance value smaller than a difference between said first and second electric resistance values.
2. The thin film magnetic memory device according to claim 1 , wherein said resistance portion includes a field effect transistor receiving a variable control voltage at its gate.
3. The thin film magnetic memory device according to claim 1 , wherein said dummy resistance adding circuit selects one of said first and second data lines to which said resistance portion is connected, according to a part of a row address.