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    • 2. 发明专利
    • Determining a cell state of a resistive memory cell
    • GB2524534A
    • 2015-09-30
    • GB201405374
    • 2014-03-26
    • IBM
    • PAPANDREOU NIKOLAOSPOZIDIS CHARALAMPOSSTANISAVLJEVIC MILOSSEBASTIAN ABU
    • G11C13/00G11C11/56
    • A device and method for determining the cell state of a resistive memory cell (such as a phase change memory PCM cell) having a plurality M of programmable cell states. The device comprises a sensing circuit 110, a settling circuit (S2,150) a prebiasing circuit 130, 131 S1 150, and a resistor Ro, 150 coupled in parallel to the resistive memory cell 200, wherein the resistor is configured to reduce the effective resistance seen by the pre biasing circuit, hence reducing the effective RC time constant of the line and reducing the overall settling time. The sensing circuit is configured to sense a sensing voltage of the resistive memory cell and output a resultant value in response to the sensing voltage which is indicative for the actual cell state. The settling circuit is configured to rapidly settle the sensing voltage to a certain target voltage representing one of the M programmable cell states. The pre biasing circuit 130 is configured to rapidly pre bias a bitline capacitance of the resistive memory cell such that the sensing voltage is close to the certain target voltage. The resistance Ro 150 may be between five and fifteen times smaller than the highest resistance value of the resistive memory cell or PCM cell. A controller (5 figure 1) activates switches S1,S2,S3 to enable pre-bias, settling and sampling modes. The controller also feeds, during the pre bias phase, a number N of gradually rising biasing voltages Vo to the pre bias circuit and bitline by means of a source follower clamping or limiter circuit 131.
    • 5. 发明专利
    • Estimation of level-thresholds for memory cells
    • GB2527318A
    • 2015-12-23
    • GB201410808
    • 2014-06-17
    • IBM
    • MITTELHOLZER THOMASPAPANDREOU NIKOLAOSPARNELL THOMASPOZIDIS CHARALAMPOSSTANISAVLJEVIC MILOS
    • G11C11/56G06F11/10G11C13/00G11C16/26
    • Apparatus and method for determining level-thresholds (5 figure 1) for q-level (multi level) memory cells such as NAND FLASH or Phase Change Memory cells. A group of the memory cells are read to obtain respective read signal components 20. The read signal components are processed in dependence on signal level 21 to produce a signal level vector (figure 3), comprising a series of elements, indicative of the distribution of read signal components in order of signal level. A plurality of possible sets of q−1 elements corresponding, respectively, to q−1 level-thresholds which partition the signal level vector into q segments, is then defined 22. The q−1 level-thresholds for the group of memory cells are then determined by selecting from the possible sets that set for which a predetermined difference function 23, dependent on differences in signal level for elements in each of said q segments for the set, has an optimum value. For example the difference function may be dependent on differences in signal level of the elements within the q segments and the optimum threshold values chosen would be based on minimizing the overall difference values between all considered elements. The first and second threshold estimation process may include hierarchical dichotomization. A computer program method for the implementation of the threshold estimation method is also included.