Abstract: A phase-change memory device, comprising: a memory array of PCM cells, a variable current generator, and a sense amplifier. The current generator comprises a reference array of PCM cells programmed in SET resistance state. The phase-change memory device further comprises a decoder for addressing each cell of the reference array so that a respective plurality of SET current signals is generated through the plurality of reference cells; and a controller configured to receive at input said SET current signals, select a number of SET current signals having the lowest current values among the plurality of SET current signals, calculate a mean value of said lowest current values, and adjust the reference current to be lower than said mean value.

Abstract: A phase-change memory device, comprising: a memory array of PCM cells, a variable current generator, and a sense amplifier. The current generator comprises a reference array of PCM cells programmed in SET resistance state. The phase-change memory device further comprises a decoder for addressing each cell of the reference array so that a respective plurality of SET current signals is generated through the plurality of reference cells; and a controller configured to receive at input said SET current signals, select a number of SET current signals having the lowest current values among the plurality of SET current signals, calculate a mean value of said lowest current values, and adjust the reference current to be lower than said mean value.

Abstract: According to an embodiment, an operational amplifier includes a first amplifier stage coupled between an input node and an intermediate node, a second amplifier stage coupled between the intermediate node and an output node, a compensation capacitor having a first terminal coupled to the intermediate node and a second terminal, and a compensation amplifier coupled between the output node and the second terminal. The compensation amplifier has a positive gain greater than one.

Abstract: According to an embodiment, an operational amplifier includes a first amplifier stage coupled between an input node and an intermediate node, a second amplifier stage coupled between the intermediate node and an output node, a compensation capacitor having a first terminal coupled to the intermediate node and a second terminal, and a compensation amplifier coupled between the output node and the second terminal. The compensation amplifier has a positive gain greater than one.

Abstract: A method for programming multilevel PCM cells envisages: forming an amorphous region of amorphous phase change material in a storage element of a PCM cell by applying one or more reset pulse; and forming a conductive path of crystalline phase change material through the amorphous region by applying one or more set pulse, a size of the conductive path defining a programmed state of the PCM cell and an output electrical quantity associated thereto, and being controlled by the value of the reset pulse and set pulse. The step of forming an amorphous region envisages adaptively and iteratively determining, during the programming operations, a value of the reset pulse optimized for electrical and/or physical properties of the PCM cell, and in particular determining a minimum amplitude value of the reset pulse, which allows programming a desired programmed state and a desired value of the output electrical quantity.

Abstract: A method for programming multilevel PCM cells envisages: forming an amorphous region of amorphous phase change material in a storage element of a PCM cell by applying one or more reset pulse; and forming a conductive path of crystalline phase change material through the amorphous region by applying one or more set pulse, a size of the conductive path defining a programmed state of the PCM cell and an output electrical quantity associated thereto, and being controlled by the value of the reset pulse and set pulse. The step of forming an amorphous region envisages adaptively and iteratively determining, during the programming operations, a value of the reset pulse optimized for electrical and/or physical properties of the PCM cell, and in particular determining a minimum amplitude value of the reset pulse, which allows programming a desired programmed state and a desired value of the output electrical quantity.

Abstract: A memory device having a reading configuration and including a plurality of memory cells, arranged in rows and columns, memory cells arranged on the same column having respective first terminals connected to a same bit line and memory cells arranged on the same row having respective second terminals selectively connectable to a same word line; a supply line providing a supply voltage; a column addressing circuit and a row addressing circuit for respectively addressing a bit line and a word line corresponding to a memory cell selected for reading in the reading configuration. The column addressing circuit is configured to bias the addressed bit line corresponding to the selected memory cell substantially at the supply voltage in the reading configuration.

Abstract: A phase change memory device includes a plurality of phase-change memory cells, arranged in rows and columns, phase-change memory cells arranged on the same column being connected to a same bit line; a plurality of first selectors, each coupled to a respective phase-change memory cell; an addressing circuit for selectively addressing at least one of the bit lines, one of the first selectors, and the phase-change memory cell connected to the addressed bit line and to the addressed first selector; and a regulated voltage supply circuit, selectively connectable to the addressed bit line, for supplying a bit line voltage. The bit line voltage is correlated to a first control voltage on the addressed first selector, coupled to the addressed phase-change memory cell.

Abstract: Described is an error control method for multilevel memory cells operating with a variable number of storage levels. The method includes: receiving a first information word having k input symbols each in a first base; converting the first information word into a second base by converting the input symbols into input symbols in the second base; encoding the converted first information word into a first codeword having k+n coded symbols in the second base; and writing the first codeword into the multilevel memory cells. The encoding step may include generating a generating matrix and multiplying the first information word by the generating matrix to produce the first codeword.

Abstract: A memory device having a reading configuration and including a plurality of memory cells, arranged in rows and columns, memory cells arranged on the same column having respective first terminals connected to a same bit line and memory cells arranged on the same row having respective second terminals selectively connectable to a same word line; a supply line providing a supply voltage; a column addressing circuit and a row addressing circuit for respectively addressing a bit line and a word line corresponding to a memory cell selected for reading in the reading configuration. The column addressing circuit is configured to bias the addressed bit line corresponding to the selected memory cell substantially at the supply voltage in the reading configuration.

Abstract: A phase change memory device includes a plurality of phase-change memory cells, arranged in rows and columns, phase-change memory cells arranged on the same column being connected to a same bit line; a plurality of first selectors, each coupled to a respective phase-change memory cell; an addressing circuit for selectively addressing at least one of the bit lines, one of the first selectors, and the phase-change memory cell connected to the addressed bit line and to the addressed first selector; and a regulated voltage supply circuit, selectively connectable to the addressed bit line, for supplying a bit line voltage. The bit line voltage is correlated to a first control voltage on the addressed first selector, coupled to the addressed phase-change memory cell.

Abstract: A charge pump circuit, connected between a first voltage reference and an output terminal, comprises at least two parallel-coupled stages having an elementary charge pump circuit connected between said first voltage reference and said output terminal, and adjustment circuitry connected between said output terminal and respective control terminals of said at least two stages. This adjustment circuitry is arranged to select for actuation an appropriate combination of these elementary stages according to the current absorbed from a load connected to the output terminal.

Abstract: A method for programming a nonvolatile memory cell envisages applying in succession, to the gate terminal of the memory cell, a first and a second programming pulse trains with pulse amplitude increasing in staircase fashion, in which the amplitude increment between one pulse and the next in the first programming pulse train is greater than the amplitude increment between one pulse and the next in the second programming pulse train. The programming method envisages applying, to the gate terminal of the memory cell and before the first programming pulse train, a third programming pulse train with pulse amplitude increasing in staircase fashion, in which the amplitude increment between one pulse and the next may be less than the amplitude increment in the first programming pulse train and substantially equal to the amplitude increment in the second programming pulse train, or else may be greater than the amplitude increment in the first programming pulse train.

Abstract: An analog-to-digital conversion method and device for a multilevel non-volatile memory device that includes a multilevel memory cell. The method comprises a first step of converting the most significant bits contained in the memory cell, followed by a second step of converting the least significant bits. The first step is completed within a time interval corresponding to the rise transient of the gate voltage, and the second step is initiated at the end of the transient. Also disclosed is a scheme for error control coding in multilevel Flash memories. The n bits stored in a single memory cell are organized in different “bit-layers”, which are independent from one another. Error correction is carried out separately for each bit-layer. The correction of any failure in a single memory cell is achieved by using a simple error control code providing single-bit correction, regardless of the number of bits stored in a single cell.

Abstract: The voltage generator comprises a negative feedback loop including a programmable voltage divider having a feedback node. The voltage divider comprises a programmable resistor disposed between the output of the voltage generator and the feedback node and having variable resistance. The programmable resistor includes a fixed resistor and a plurality of additional resistors arranged in series with each other and defining a plurality of intermediate nodes. The additional resistors may be selectively connected by means of switches disposed between the output of the voltage generator and a respective intermediate node so as to define an output voltage V0 programmable on the basis of command signals supplied to the switches.

Abstract: A charge pump circuit, connected between a first voltage reference and an output terminal, comprises at least two stages comprising an elementary charge pump circuit connected between said first voltage reference and said output terminal, and adjustment circuitry connected between said output terminal and respective control terminals of said at least two stages. This circuitry is arranged to select for actuation an appropriate combination of these elementary stages according to the current absorbed from a load connected to the output terminal.

Abstract: A reading circuit for semiconductor non-volatile memories connected to at least one selected cell and at least one reference cell, the circuit including current/voltage conversion circuits receiving a first current flowing through the selected cell and a second current flowing through the reference cell and providing respectively on a first circuit node a first selected cell voltage and on a second node a second reference cell voltage, at least one differential amplifier connected at the input of the first and the second nodes and having an output terminal to provide a logic signal correlated to the selected cell information, a first voltage-controlled discharge switch circuit connected to the first node and to a voltage reference, a second switch circuit connected to the second node and the voltage reference, and first and second voltage comparator circuits receiving the first selected cell voltage and the second reference cell voltage.

Abstract: A voltage regulator having a comparator with an output terminal that is the output of the regulator, terminals for connection to a voltage supply, a source of a reference voltage connected to an input terminal of the comparator, and a feedback circuit connected between the output terminal and the other input terminal of the comparator. To prevent transients upon the transition from the standby state to the active state, there is provided a second reference-voltage source that provides a reference voltage substantially equal to that of the first source, a switch for connecting the second source to the other input terminal of the comparator, and a control circuit that can activate the supply of the regulator and can close the switch for a predetermined period of time when the supply of the regulator is activated.

Abstract: A multilevel nonvolatile memory includes a supply line (28) supplying a supply voltage (VDD), a voltage boosting circuit (26) supplying a boosted voltage (Vp), higher than the supply voltage (VDD), a boosted line (30) connected to the voltage boosting circuit (26) and a reading circuit (25) including at least one comparator (35). The comparator (35) includes a first and a second input (35a, 35b), a first and a second output (45a, 45b), at least one amplification stage (40) connected to the boosted line (30), and a boosted line latch stage (41) connected to the supply line (28).

Abstract: A sensing circuit for serial dichotomic sensing of multiple-level memory cells which can take one programming level among a plurality of m=2n (n>=2) different programming levels, comprises biasing means for biasing a memory cell to be sensed in a predetermined condition, so that the memory cell sinks a cell current with a value belonging to a plurality of m distinct cell current values, each cell current value corresponding to one of the programming levels, a current comparator for comparing the cell current with a reference current generated by a variable reference current generator, and a successive approximation register supplied with an output signal of the current comparator and controlling the variable reference current generator.