A selection scheme for crosspoint memory is described. In one example, the selection voltage applied across the memory cell is slowly ramped up. Once the memory cell thresholds, the voltage is reduced to a level for performing the read or write operation. Reducing the voltage once the specific cell has been selected (e.g., thresholds) minimizes the additional transient current which might be generated by further increasing the selection bias applied during read or write operation. The reduction in transient current can lead to an improvement in read disturb and write endurance issues. The selection ramp-rate and bias post-selection can be set differently depending on the cell location inside the memory array to further improve cell performance.

Apparatus and methods utilize a replica circuit to generate a voltage for programming of a memory cell, such as a memory cell of a phase-change memory (PCM). Current passing through a circuit including the memory cell to be programmed is mirrored in a scaled or unscaled manner, and provided as an input to the replica circuit. The replica circuit represents voltage drops that should be encountered when programming the memory cell. An input voltage is also provided to the replica circuit, which affects the voltage drop within the replica circuit that represents the voltage drop of the cell. The voltage drop across the replica circuit can then be mirrored and provided to bias the circuit including the memory cell.

A selection scheme for crosspoint memory is described. In one example, the selection voltage applied across the memory cell is slowly ramped up. Once the memory cell thresholds, the voltage is reduced to a level for performing the read or write operation. Reducing the voltage once the specific cell has been selected (e.g., thresholds) minimizes the additional transient current which might be generated by further increasing the selection bias applied during read or write operation. The reduction in transient current can lead to an improvement in read disturb and write endurance issues. The selection ramp-rate and bias post-selection can be set differently depending on the cell location inside the memory array to further improve cell performance.

A selection scheme for crosspoint memory is described. In one example, the selection voltage applied across the memory cell is slowly ramped up. Once the memory cell thresholds, the voltage is reduced to a level for performing the read or write operation. Reducing the voltage once the specific cell has been selected (e.g., thresholds) minimizes the additional transient current which might be generated by further increasing the selection bias applied during read or write operation. The reduction in transient current can lead to an improvement in read disturb and write endurance issues. The selection ramp-rate and bias post-selection can be set differently depending on the cell location inside the memory array to further improve cell performance.

In one aspect, the invention concerns a memory system that compensates for power level variations in sense amplifiers for multilevel memory. For example, a compensation circuit can be employed to compensate for current or voltage variations in the power supplied to multilevel memory sense amplifiers. As another example, compensation can be accomplished by application of a bias voltage to the power supply. Another example is a sense amplifier configured with improved input common mode voltage range. Such sense amplifiers can be two-pair and three-pair sense amplifiers. Further examples of the invention include more simplified sense amplifier configurations, and sense amplifiers having reduced leakage current.

Apparatus and methods utilize a replica circuit to generate a voltage for programming of a memory cell, such as a memory cell of a phase-change memory (PCM). Current passing through a circuit including the memory cell to be programmed is mirrored in a scaled or unscaled manner, and provided as an input to the replica circuit. The replica circuit represents voltage drops that should be encountered when programming the memory cell. An input voltage is also provided to the replica circuit, which affects the voltage drop within the replica circuit that represents the voltage drop of the cell. The voltage drop across the replica circuit can then be mirrored and provided to bias the circuit including the memory cell.

A detection circuit that can detect a two-terminal memory cell changing state. For example, in response to electrical stimuli, a memory cell will change state, e.g., to a defined higher resistance state or a defined lower resistance state. Other, techniques do not detect this state change until after the stimuli is completed and a subsequent sensing operation (e.g., read pulse) is performed. The detection circuit can detect the state change during application of the electrical stimuli that cause the state change and can do so by comparing the magnitudes or values of two particular current parameters.

In one aspect, the invention concerns a memory system that compensates for power level variations in sense amplifiers for multilevel memory. For example, a compensation circuit can be employed to compensate for current or voltage variations in the power supplied to multilevel memory sense amplifiers. As another example, compensation can be accomplished by application of a bias voltage to the power supply. Another example is a sense amplifier configured with improved input common mode voltage range. Such sense amplifiers can be two-pair and three-pair sense amplifiers. Further examples of the invention include more simplified sense amplifier configurations, and sense amplifiers having reduced leakage current.

Apparatus and methods utilize a replica circuit to generate a voltage for programming of a memory cell, such as a memory cell of a phase-change memory (PCM). Current passing through a circuit including the memory cell to be programmed is mirrored in a scaled or unscaled manner, and provided as an input to the replica circuit. The replica circuit represents voltage drops that should be encountered when programming the memory cell. An input voltage is also provided to the replica circuit, which affects the voltage drop within the replica circuit that represents the voltage drop of the cell. The voltage drop across the replica circuit can then be mirrored and provided to bias the circuit including the memory cell.

Apparatus and methods utilize a replica circuit to generate a voltage for programming of a memory cell, such as a memory cell of a phase-change memory (PCM). Current passing through a circuit including the memory cell to be programmed is mirrored in a scaled or unscaled manner, and provided as an input to the replica circuit. The replica circuit represents voltage drops that should be encountered when programming the memory cell. An input voltage is also provided to the replica circuit, which affects the voltage drop within the replica circuit that represents the voltage drop of the cell. The voltage drop across the replica circuit can then be mirrored and provided to bias the circuit including the memory cell.