摘要:
Methods of operating memory arrays are described. In various embodiments, a method includes determining a pattern to be written to a memory array, the pattern comprising both data bits having sensitive information to be stored and data bits having a state that is unimportant to the sensitive information to be stored, and writing the pattern to the memory array. Other methods of operation are also described.
摘要:
A read circuit for reading at least one memory cell adapted to storing a logic value, the at least one memory cell including: a storage element made of a phase-change material; and an access element for coupling the storage element to the read circuit in response to a selection of the memory cell, the read circuit including: a sense current supply arrangement for supplying a sense current to the at least one memory cell; and at least one sense amplifier for determining the logic value stored in the memory cell on the basis of a voltage developing thereacross, the at least one sense amplifier comprising a voltage limiting circuit for limiting the voltage across the memory cell for preserving the stored logic value, wherein the voltage limiting circuit includes a current sinker for sinking a clamping current, which is subtracted from the sense current and depends on the stored logic value.
摘要:
A phase change memory device includes a bitline biasing unit; and a bitline selection unit connecting a selected bitline to the bitline biasing unit and disconnecting deselected bitlines from the bitline biasing unit in an operative condition. A bitline discharge unit is connected to the bitlines to discharge leakage currents in the bitlines. The bitline discharge unit has a voltage regulation unit and a plurality of bitline discharge switches coupled between the voltage regulation unit and a respective bitline. The bitline discharge switches are controlled to connect the deselected bitlines to the voltage regulation unit and to disconnect the selected bitline from the voltage regulation unit. The voltage regulation unit comprises a PMOS transistor coupled between a regulated voltage bus and a reference potential line. The regulated voltage bus is connected to the bitline discharge switches and the control terminal of the PMOS transistor is biased to a constant voltage.
摘要:
A read current high enough to threshold a phase change memory element may be used to read the element without thresholding the memory element. The higher current may improve performance in some cases. The memory element does not threshold because the element is read and the current stopped prior to triggering the memory element.
摘要:
According to a method for multilevel reading of a phase change memory cell a bit line (9) and a PCM cell (2) are first selected and a first bias voltage (VBL, V00) is applied to the selected bit line (9). A first read current (IRD00), that flows through the selected bit line (9) in response to the first bias voltage (VBL, V00), is compared with a first reference current (I00). The first reference current (I00) is such that the first read current (IRD00) is lower than the first reference current (I00), when the selected PCM cell (2) is in a reset state, and is otherwise greater. It is then determined whether the selected PCM cell (2) is in the reset state, based on comparing the first read current (IRD00) with the first reference current (I00). A second bias voltage (VBL, V01), greater than the first bias voltage (VBL, V00), is applied to the selected bit line (9) if the selected PCM cell (2) is not in the reset state.
摘要:
Multilevel phase change memory cells may be programmed forming amorphous regions of amorphous phase change material in a storage region of the phase change memory cell. Crystalline paths of crystalline phase change material are formed through the amorphous regions of amorphous phase change material. Lengths of the crystalline paths are controlled so that at least a first crystalline path has a first length in a first programming state and a second crystalline path has a second length, different from the first length, in a second programming state.
摘要:
A current mirror circuit is provided with a first current mirror including a first and a second mirror transistors sharing a common control terminal; the first mirror transistor has a conduction terminal for receiving, during a first operating condition, a first reference current, and the second mirror transistor has a respective conduction terminal for providing, during the first operating condition, a mirrored current based on the first reference current. The current mirror circuit is provided with a switching stage operable to connect the control terminal to the conduction terminal of the first mirror transistor during the first operating condition, and to disconnect the control terminal from the same conduction terminal of the first mirror transistor, and either letting it substantially floating or connecting it to a reference voltage, during a second operating condition, in particular a condition of stand-by.
摘要:
A semiconductor memory device, including a plurality of programmable memory cells each one adapted to be brought into one among at least a first status and a second status, said plurality of memory cells including memory cells intended to store data, and means for accessing the memory cells for reading/modifying their status. At least one memory cell in said plurality is used as detector memory cell, and control means operatively associated with the at least one detector memory cell are provided, said control means being adapted to establishing a potential loss of the data stored in the memory cells of said plurality based on a detected first status of the at least one detector memory cell.
摘要:
A biasing circuit for use in a non-volatile memory device is coupled to the row decoder and to the column decoder to supply a first and at least a second biasing voltage for the word and bit lines, and includes a first voltage booster having a first input coupled to receive a supply voltage, a second input coupled to receive a reference voltage, and an output coupled to one of the row decoder and the column decoder to supply the first biasing voltage. A second voltage booster has a first input coupled to receive the supply voltage, a second input coupled to the output of the first voltage booster to receive the first biasing voltage, and an output coupled to the other of the row decoder and the column decoder to supply the second biasing voltage.
摘要:
A phase change memory includes a temperature sensor having a resistance variable with temperature with the same law as a phase-change storage element. The temperature sensor is formed by a resistor of chalcogenic material furnishing an electrical quantity that reproduces the relationship between the resistance of a phase change memory cell and temperature; the electrical quantity is processed so as to generate reference quantities as necessary for writing and reading the memory cells. The chalcogenic resistor has the same structure as a memory cell and is programmed with precision, preferably in the reset state.