Abstract: Systems, circuits and methods for controlling the word line voltage applied to word line transistors in Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM) are disclosed. One embodiment is directed to a STT-MRAM including a bit cell having a magnetic tunnel junction (MTJ) and a word line transistor. The bit cell is coupled to a bit line and a source line. A word line driver is coupled to a gate of the word line transistor. The word line driver is configured to provide a word line voltage greater than a supply voltage below a transition voltage of the supply voltage and to provide a voltage less than the supply voltage for supply voltages above the transition voltage.

Abstract: A level shifting circuit has a pair of assist circuits. The level shifting circuit includes an input point, an output point, a pair of cross-coupled PMOS transistors coupled to the output point, and a pair of NMOS transistors coupled between the input and output points. Each assist circuit includes a pair of PMOS transistors, one responsive to an input applied to the input point, the other responsive to the drain voltage of one of the NMOS transistors. The assist circuits temporarily weaken the cross-coupled PMOS transistors when an input changes from low to high, or from high to low. The assist circuits also transiently boost the output.

Abstract: Exemplary embodiments of the invention are directed to magnetic elements including a passivation layer for isolation from other on-chip elements. One embodiment is directed to an apparatus comprising a magnetic tunnel junction (MTJ) element. The MTJ element comprises: a first ferromagnetic layer; a second ferromagnetic layer; an insulating layer disposed between the first and second ferromagnetic layers; and an MTJ passivation layer forming protective sidewalls disposed adjacent to the first ferromagnetic layer, the second ferromagnetic layer, and the insulating layer.

Abstract: In a particular embodiment, a memory device is disclosed that includes a memory cell including a resistance-based memory element coupled to an access transistor. The access transistor has a first oxide thickness to enable operation of the memory cell at an operating voltage. The memory device also includes a first amplifier configured to couple the memory cell to a supply voltage that is greater than a voltage limit to generate a data signal based on a current through the memory cell. The first amplifier includes a clamp transistor that has a second oxide thickness that is greater than the first oxide thickness. The clamp transistor is configured to prevent the operating voltage at the memory cell from exceeding the voltage limit.

Abstract: A level shifting circuit has a pair of assist circuits. The level shifting circuit includes an input point, an output point, a pair of cross-coupled PMOS transistors coupled to the output point, and a pair of NMOS transistors coupled between the input and output points. Each assist circuit includes a pair of PMOS transistors, one responsive to an input applied to the input point, the other responsive to the drain voltage of one of the NMOS transistors. The assist circuits temporarily weaken the cross-coupled PMOS transistors when an input changes from low to high, or from high to low. The assist circuits also transiently boost the output.

Abstract: Systems and methods of selectively applying negative voltage to word lines during memory device read operation are disclosed. In an embodiment, a memory device includes a word line logic circuit coupled to a plurality of word lines and adapted to selectively apply a positive voltage to a selected word line coupled to a selected memory cell that includes a magnetic tunnel junction (MTJ) device and to apply a negative voltage to unselected word lines.

Abstract: A semiconductor memory device includes address signal level shifters configured to transform a low level address signal into a higher level address signal. A decoder is configured to receive the higher level address signal and, in response, provide word line signals. Write drivers receive low level data input signals and configure bitlines in response to the received input. Memory cells are responsive to the word line signals and to the configured bit lines for storing data therein.

Abstract: Systems and methods of controlled value reference signals of resistance based memory circuits are disclosed. In a particular embodiment, a circuit device is disclosed that includes a first input configured to receive a reference control signal. The circuit device also includes an output responsive to the first input to selectively provide a controlled value reference voltage to a sense amplifier coupled to a resistance based memory cell.

Abstract: Systems, circuits and methods for controlling write operations in Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM) are disclosed. A reduced bit cell size is achieved by arranging the source lines (SL) substantially in parallel with the word lines (WL) and substantially perpendicular to the bit lines (BL). Further, in one embodiment during a write operation, a high logic/voltage level is applied to the bit lines of unselected bit cells to prevent an invalid write operation.

Abstract: Systems and methods of resistance based memory circuit parameter adjustment are disclosed. In a particular embodiment, a method of determining a set of parameters of a resistance based memory circuit includes selecting a first parameter based on a first predetermined design constraint of the resistance based memory circuit and selecting a second parameter based on a second predetermined design constraint of the resistance based memory circuit. The method further includes performing an iterative methodology to adjust at least one circuit parameter of a sense amplifier portion of the resistance based memory circuit by selectively assigning and adjusting a physical property of the at least one circuit parameter to achieve a desired sense amplifier margin value without changing the first parameter or the second parameter.

Abstract: A mixed serial-parallel content addressable memory (CAM) includes serial CAM cells and parallel CAM cells that are arranged in multiple (N) columns and multiple (M) rows. Each row includes at least one serial CAM cell and at least two parallel CAM cells. The M rows are searched in parallel. For each row, the serial CAM cells are searched sequentially, and the parallel CAM cells are selectively searched in parallel. The CAM further includes a driver that generates search lines for the N columns of CAM cells, one search line per column. The driver sets the search lines to an N-bit value to search for in the CAM. Prior to each search operation, the driver presets at least one search line for at least one column of serial CAM cells to precharge a match line for each row.

Abstract: Systems and methods of selectively applying negative voltage to word lines during memory device read operation are disclosed. In an embodiment, a memory device includes a word line logic circuit coupled to a plurality of word lines and adapted to selectively apply a positive voltage to a selected word line coupled to a selected memory cell that includes a magnetic tunnel junction (MTJ) device and to apply a negative voltage to unselected word lines.

Abstract: Systems and methods of leakage control in an asynchronous pipeline are disclosed. In an embodiment, a signal is received from a preceding stage at an operative stage of an asynchronous circuit device, and a switch associated with the operative stage is activated in response to the control signal being sent to the operative stage to enable power to the operative stage.

Abstract: In a particular embodiment, a memory device includes a first memory cell and a second memory cell. The memory device also includes a first bit line associated with the first memory cell and a second bit line associated with the second memory cell. The memory device also includes a source line coupled to the first memory cell and coupled to the second memory cell.

Abstract: A memory device utilizes selective precharge and charge sharing to reduce a bit line voltage before accessing a bit cell. A reduction in bit line voltage is achieved by precharging different sections of the bit line to different voltages (e.g., a supply voltage and ground) and using charge sharing between these sections. Read stability improves as a result of the reduction of bit line voltage. The relative capacitance difference between bit line sections determines the bit line voltage after charge sharing. Thus, the memory device is tolerant to process or temperature variations. The bit line voltage may be controlled in design by selecting the sections that are precharged to supply voltage or ground.

Abstract: Systems, circuits and methods for adapting word line (WL) pulse widths used in memory systems are disclosed. One embodiment of the invention is directed to an apparatus comprising a memory system. The memory system comprises: a memory operating according to a wordline (WL) pulse with an associated WL pulse width; a built-in self-test (BIST) unit that interfaces with the memory, the BIST unit being configured to run a self-test of the internal functionality of the memory and provide a signal indicating if the memory passed or failed the self-test; and an adaptive WL control circuit that interfaces with the BIST unit and the memory, the adaptive WL control circuit being configured to adjust the WL pulse width of the memory based on the signal provided by the BIST unit.

Abstract: Systems, circuits and methods for read operations in Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM) are disclosed. A plurality of bit cells, each coupled to one of a plurality of bit lines, word lines and source lines are provided. A plurality of precharge transistors corresponding to one of the plurality of bit lines are configured to discharge the bit lines to ground prior to a read operation.

Abstract: A system and method for sensing a data state stored by a memory cell that includes coupling a first digit line and a second digit line to a precharge voltage and further coupling a memory cell to the first digit line. At least one digit line other than the first and second digit lines is driven to a reference voltage level and the at least one digit line is coupled to the second digit line to establish a reference voltage in the second digit line. A voltage differential is sensed between the first digit line and the second digit line, and a data state based on the voltage differential is latched in response.

Abstract: Systems, circuits and methods for determining read and write voltages for a given word line transistor in Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM) are disclosed. A first voltage can be supplied to the write operations so that the write operations occur in the saturation region of the word line transistor. A second voltage, which is less than the first voltage, can be supplied for read operations so that the read operations occur in the linear region of the word line transistor.

Abstract: Systems, circuits and methods for reducing read disturbances in Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM) are disclosed. A resistive element can be used during the read operation to control the read current and control read disturbances. An isolation element can be used to isolate the resistive element from the circuit during write operations.