Static information storage and retrieval – Addressing – Particular decoder or driver circuit
Patent
1997-02-18
1998-08-11
Fears, Terrell W.
Static information storage and retrieval
Addressing
Particular decoder or driver circuit
365 66, 365171, G11C 1300
Patent
active
057936978
ABSTRACT:
A sensing circuit reads the magnetic state of individual memory cells making up a nonvolatile magnetic random access memory (MRAM) array. Each memory cell is a magnetic tunnel junction (MTJ) element and a diode electrically connected in series. Each MTJ is formed of a pinned ferromagnetic layer whose magnetization direction is prevented from rotating, a free ferromagnetic layer whose magnetization direction is free to rotate between states of parallel and antiparallel to the fixed magnetization of the pinned ferromagnetic layer, and an insulating tunnel barrier between and in contact with the two ferromagnetic layers. The memory cells in the array are controlled by only two lines, and the write currents to change the magnetic state of an MTJ, by use of the write currents' inherent magnetic fields to rotate the magnetization of the free layer, do not pass through the tunnel barrier layer. The magnetic state of a memory cell is read by reducing the voltage on one of the lines while the voltage on the other line is clamped.
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Berthold Thomas R.
Fears Terrell W.
International Business Machines - Corporation
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