Abstract:
A phase change memory (20) has an array (1) formed by a plurality of cells (2), each including a memory element (3) of calcogenic material and a selection element (4) connected in series to the memory element; a plurality of address lines (11) connected to the cells; a write stage (24) and a reading stage (25) connected to the array. The write stage (24) is formed by current generators (45), which supply preset currents to the selected cells (2) so as to modify the resistance of the memory element (3). Reading takes place in voltage, by appropriately biasing the selected cell and comparing the current flowing therein with a reference value.
Abstract:
A nonvolatile memory device (10'; 10") is described comprising a memory array (11), a row decoder (12) and a column selector (13) for addressing the memory cells (16) of the memory array (11), and a biasing stage (22; 36, 28) for biasing the array access device terminal of the addressed memory cell (16). The biasing stage (22; 36 28) is arranged between the column selector (13) and the memory array (11) and comprises a biasing transistor (22; 36) having a drain terminal connected to the column selector (13), a source terminal connected to the array access device terminal of the addressed memory cell (16), and a gate terminal receiving a logic driving signal, the logic levels of which are defined by precise and stable voltages and are generated by a logic block (31) and an output buffer (32) cascaded together. The output buffer (32) may be supplied with either a read voltage (VREAD) or a program voltage (VPROG) supplied by a multiplexer (33). The biasing transistor (22; 36) may be either included as part of the column selector (13) and formed by the selection transistor (22) which is closest to the addressed memory cell (16) or distinct from the selection transistors (20, 21, 22) of the column selector (13).
Abstract:
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 (20) of chalcogenic material furnishing an electrical quantity (V(T), I(T)) that reproduces the relationship between the resistance of a phase change memory cell and temperature; the electrical quantity is processed (21) so as to generate reference quantities as necessary for writing and reading the memory cells. The chalcogenic resistor (20) has the same structure as a memory cell and is programmed with precision, preferably in the reset state.
Abstract:
A nonvolatile memory device (10'; 10") is described comprising a memory array (11), a row decoder (12) and a column selector (13) for addressing the memory cells (16) of the memory array (11), and a biasing stage (22; 36, 28) for biasing the array access device terminal of the addressed memory cell (16). The biasing stage (22; 36 28) is arranged between the column selector (13) and the memory array (11) and comprises a biasing transistor (22; 36) having a drain terminal connected to the column selector (13), a source terminal connected to the array access device terminal of the addressed memory cell (16), and a gate terminal receiving a logic driving signal, the logic levels of which are defined by precise and stable voltages and are generated by a logic block (31) and an output buffer (32) cascaded together. The output buffer (32) may be supplied with either a read voltage (VREAD) or a program voltage (VPROG) supplied by a multiplexer (33). The biasing transistor (22; 36) may be either included as part of the column selector (13) and formed by the selection transistor (22) which is closest to the addressed memory cell (16) or distinct from the selection transistors (20, 21, 22) of the column selector (13).
Abstract:
The memory device (10) comprises a memory array (2) having an organisation of the type comprising global word lines (4) and local word lines (6), a global row decoder (8) addressing the global word lines (4), a local row decoder (12) addressing the local word lines (6), a global power supply stage (22) supplying the global row decoder (8), and a local power supply stage (24) supplying the local row decoder (12).