Abstract: An apparatus for improving stability of a magnetoresistive random access memory over process and operational variations includes a current reference circuit that provides a reference current control signal to variable analog control circuitry. The variable analog control circuitry is connected to receive control signals from the current reference. The variable analog control circuitry generates a word current reference signal in response to the reference current control signal and further generates a source current reference signal in response to the reference current control signal. At least one word current source is connected to receive the word current reference signal. At least one sense current source is connected to receive the source current reference signal.

Abstract: A method to adjust an operating parameter of a magnetoresistive random access memory having a tunable circuit, such as a bias control circuit, provides for measuring the operating parameter, such as a word current or sense current, of the magnetoresistive random access memory to obtain a measured operating parameter result and tuning the tunable circuit, such as with trimmable resistors, based on the measured operating parameter result. A method is also provided to adjust an operating parameter of a wafer of magnetic random access memories each having a tunable circuit by measuring the operating parameter one or more of the magnetic random access memories to obtain a measured operating parameter result and tuning some or all of the tunable circuits based on the measured operating parameter result.

Abstract: A magnetic random access memory (10) with equalization has a plurality of magnetic memory elements that perform a memory operation. A word line magnetically activates at least one magnetic memory element. A sense line detects the state of the at least one magnetic memory element. A word line driver is connected to the word line to drive a current on the word line during the memory operation. A word line equalizer is connected to the word line to equalize the word line during the non-memory operations.

Abstract: A word current source (445) for a magnetoresistive random access memory circuit (420) includes an n-channel transistor (430) including a gate, a source and a drain, where the source is coupled to a supply ground, and the drain is coupled to the magnetoresistive random access memory circuit. A positive supply voltage is coupled to the magnetoresistive random access memory circuit (420) so as to allow current to flow through the magnetoresistive random access memory circuit (420) when an activation signal is applied to the gate by the control circuit.

Abstract: A current controlled sense current source having a current source with a stable reference current output is provided with a sense current source having a sense current reference input connected to the stable reference current output with the sense current source having a sense current output. A current controlled word current source comprising a current source having a stable reference current output is also provided with a word current source having a word current reference input connected to the stable reference current output with the word current source having a word current output.

Abstract: MRAM sensing operations use a word line (80, 82, 84, 86) and a sense current to detect the state of a bit (70, 72). The bit (70, 72) has a high resistance or a low resistance state. Using multiple sub bits (30, 32, 34, 36, 38, 40, 42, 44) in each bit (70, 72) increases the difference between the high resistance and low resistance state in proportion to the number of sub bits (30, 32, 34, 36, 38, 40, 42, 44) in each bit (70, 72). Multiple sub bits (30, 32, 34, 36, 38, 40, 42, 44) also provide redundancy in the event of failure of a sub bit (30, 32, 34, 36, 38, 40, 42, 44). The MRAM can be designed to function with one or more sub bits (30, 32, 34, 36, 38, 40, 42, 44) being defective.

Abstract: A word current source (445) for a magnetoresistive random access memory circuit (420) includes an n-channel transistor (430) including a gate, a source and a drain, where the source is coupled to a supply ground, and the drain is coupled to the magnetoresistive random access memory circuit. A positive supply voltage is coupled to the magnetoresistive random access memory circuit (420) so as to allow current to flow through the magnetoresistive random access memory circuit (420) when an activation signal is applied to the gate by the control circuit.

Abstract: A current controlled sense current source having a current source with a stable reference current output is provided with a sense current source having a sense current reference input connected to the stable reference current output with the sense current source having a sense current output. A current controlled word current source comprising a current source having a stable reference current output is also provided with a word current source having a word current reference input connected to the stable reference current output with the word current source having a word current output.

Abstract: A magnetic random access memory (10) with equalization has a plurality of magnetic memory elements that perform a memory operation. A word line magnetically activates at least one magnetic memory element. A sense line detects the state of the at least one magnetic memory element. A word line driver is connected to the word line to drive a current on the word line during the memory operation. A word line equalizer is connected to the word line to equalize the word line during the non-memory operations.

Abstract: An apparatus for improving stability of a magnetoresistive random access memory over process and operational variations includes a current reference circuit that provides a reference current control signal to variable analog control circuitry. The variable analog control circuitry is connected to receive control signals from the current reference. The variable analog control circuitry generates a word current reference signal in response to the reference current control signal and further generates a source current reference signal in response to the reference current control signal. At least one word current source is connected to receive the word current reference signal. At least one sense current source is connected to receive the source current reference signal.

Abstract: A method to adjust an operating parameter of a magnetoresistive random access memory having a tunable circuit, such as a bias control circuit, provides for measuring the operating parameter, such as a word current or sense current, of the magnetoresistive random access memory to obtain a measured operating parameter result and tuning the tunable circuit, such as with trimmable resistors, based on the measured operating parameter result. A method is also provided to adjust an operating parameter of a wafer of magnetic random access memories each having a tunable circuit by measuring the operating parameter one or more of the magnetic random access memories to obtain a measured operating parameter result and tuning some or all of the tunable circuits based on the measured operating parameter result.

Abstract: MRAM sensing operations use a word line (80, 82, 84, 86) and a sense current to detect the state of a bit (70, 72). The bit (70, 72) has a high resistance or a low resistance state. Using multiple sub bits (30, 32, 34, 36, 38, 40, 42, 44) in each bit (70, 72) increases the difference between the high resistance and low resistance state in proportion to the number of sub bits (30, 32, 34, 36, 38, 40, 42, 44) in each bit (70, 72). Multiple sub bits (30, 32, 34, 36, 38, 40, 42, 44) also provide redundancy in the event of failure of a sub bit (30, 32, 34, 36, 38, 40, 42, 44). The MRAM can be designed to function with one or more sub bits (30, 32, 34, 36, 38, 40, 42, 44) being defective.

Abstract: MRAM noise stabilizing and reducing apparatus and methods for MRAM sensing operations injects noise generated by activation of a word line (80, 82, 84, 86) into a sense line (128) and a reference line (130). Sense strings (20, 22, 24, 26) addressed by the word line (80, 82, 84, 86) are alternately coupled to the sense line (128) and the reference line (130). Cross coupling reduces the noise injected on the sense lines (128, 130). Cross coupling also balances the noise created by activation of the word line (80, 82, 84, 86) between the sense line (128) and reference line (130). A sense string (20, 22, 24, 26) not addressed by the word line (80, 82, 84, 86) provides a reference signal. A differential amplifier (132) includes circuitry to compare and store a difference between the sense line (128) and the reference line (130). The stored value can be further compared to a second value obtained by reversing the current on the word line (80, 82, 84, 86).