Patent ID: 9672886
Date: 2017-06-06
CPC Classifications: G11C

Claim:
1. A pre-read and write sense amplifier (PWSA) apparatus for magnetoresistive random access memory (MRAM), comprising: a write and pre-charge circuit coupled to a bit line and bit line reference and respective center node and reference signals; wherein said bit line is configured for coupling to magnetic tunnel junction (MTJ) cells in a magnetoresistive random access memory (MRAM); a differential amplifier configured for reading state of a selected one of the MTJ cells; a first data latch configured for retaining state as read by said differential amplifier, and to output that state to said write and pre-charge circuit; a second data latch configured for storing a data state to which the selected one of the MTJ cells is to be set; a control circuit coupled to said differential amplifier for performing logic and sequential operations; and a comparison circuit configured for comparing data retained by said first and second latches and outputting a comparison signal to said differential amplifier and said control circuit; wherein said control circuit is configured to generate a write pulse for a precessional write operation to the selected one of the MTJ cells only if said comparison signal indicates that data retained in said first and second latches is different; wherein said precessional write operation is performed by applying a pulse across the selected one of the MTJ cells, in which the pulse is of a selected duration to cause precession of magnetic moment in that MTJ cell to change its state from a first state to a second state, or from a second state back to a first state; and wherein said control circuit is configured for activating said differential amplifier for sensing data state in the selected one of the MTJ cells after it has been written, and in response to said comparison generating a pass/fail signal indicating if the write was successful.