Stmicroelectronics S.r.l.

Stmicroelectronics International N.v.

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Fabio Enrico Carlo Disegni

Maurizio Francesco Perroni

Davide Manfré

Marcella Carissimi

Laura Capecchi

Davide Manfre′

Emanuela Calvetti

Massimo Fidone

Vikas Rana

Michele La Placa

Federico Goller

Chantal Auricchio

Davide Manfre'

Guiseppe Scardino

Stefano Zanchi

Massimo Caruso

Giuseppe Scardino

A memory device includes programmable memory cells and a programming circuit for programming a selected memory cell to a target logic state by applying one or more programming current pulses. A temperature sensor operates to sense a temperature of the memory device. A reading circuit reads a current logic state of the selected memory cell after a predetermined programming current pulse of the programming current pulses. The reading circuit includes a sensing circuit that senses a current logic state of the selected memory cell according to a comparison between a reading electric current depending on the current logic state of the selected memory cell and a reference current. An adjusting circuit adjusts one or the other of the reading electric current and the reference electric current to be provided to the sensing circuit according to the temperature of the memory device.

Memory device

A phase-change memory device column decoder is divided into two portions that can be governed independently of one another, and the driving signals of the two portions are configured so as to guarantee comparable capacitive loads at the two inputs of a sense amplifier in both of the operations of single-ended reading and double-ended reading. In particular, during single-ended reading, the sense amplifier has a first input that receives a capacitive load corresponding to the direct memory cell selected, and a second input that receives a capacitive load associated to a non-selected complementary memory cell.

Phase change memory device, system including the memory device, and method for operating the memory device

An embodiment non-volatile memory device includes an array of memory cells in rows and columns; a plurality of local bitlines, the memory cells of each column being coupled to a corresponding local bitline; a plurality of main bitlines, each main bitline being coupleable to a corresponding subset of local bitlines; a plurality of program driver circuits, each having a corresponding output node and injecting a programming current in the corresponding output node, each output node coupleable to a corresponding subset of main bitlines. Each program driver circuit further includes a corresponding limiter circuit that is electrically coupled, for each main bitline of the corresponding subset, to a corresponding sense node whose voltage depends, during writing, on the voltage on the corresponding main bitline. Each limiter circuit turns off the corresponding programming current, in case the voltage on any of the corresponding sense nodes overcomes a reference voltage.

Non-volatile memory device with a program driver circuit including a voltage limiter

An embodiment non-volatile memory device includes an array of memory cells arranged in rows and columns; a plurality of local bitlines; and a plurality of main bitlines, each main bitline being coupleable to a corresponding subset of local bitlines. The memory cells of each column are coupled to a corresponding local bitline. The memory device further includes a column decoder, which can be controlled electronically so as to couple each main bitline to a selected local bitline of the corresponding subset of local bitlines. The column decoder couples each main bitline to two different points of the corresponding selected local bitline.

Memory device and method for coupling a main bitline to two points of a local bitline

A non-volatile memory device including an array of memory cells coupled to word lines and a row decoder, which includes a first and a second pull-down stage, which are arranged on opposite sides of the array, and include, respectively, for each word line, a corresponding first pull-down switching circuit and a corresponding second pull-down switching circuit, which are coupled to a first point and a second point, respectively, of the first word line. The row decoder moreover comprises a pull-up stage, which includes, for each word line, a corresponding pull-up switching circuit, which can be electronically controlled in order to: couple the first point to a supply node in the step of deselection of the word line; and decouple the first point from the supply node in the step of selection of the word line.

Non volatile memory device with an asymmetric row decoder and method for selecting word lines

An embodiment method for programming a differential type phase-change memory device comprises, in a first time interval, programming a direct memory cell or the respective complementary one pertaining to a first programming driver by means of a current between SET and RESET; and, in the same first time interval, simultaneously programming a direct memory cell or the respective complementary one pertaining to a second programming driver by means of the same current between SET and RESET. The method further comprises, in a second time interval, programming the other direct memory cell or the respective complementary one pertaining to the first programming driver by means of the other current between SET and RESET; and, in the same second time interval, simultaneously programming the other direct memory cell or the respective complementary one pertaining to the second programming driver by means of the same other current between SET and RESET.

Method for programming a phase-change memory device of differential type, phase-change memory device, and electronic system

In an embodiment, the column decoder of a PCM device is divided into two portions that can be governed independently of one another, and the driving signals of the two portions are configured so as to guarantee comparable capacitive loads at the two inputs of a sense amplifier in both of the operations of single-ended reading and double-ended reading. In particular, during single-ended reading, the sense amplifier has a first input that receives a capacitive load corresponding to the direct memory cell selected, and a second input that receives a capacitive load associated to a non-selected complementary memory cell.

An embodiment voltage generation circuit, for a memory having a memory array with a plurality of memory cells coupled to respective wordlines and local bit-lines, each having a storage element and selector element, a bipolar transistor being coupled to the storage element for selective flow of a cell current during reading or verifying operations, and a base terminal of the selector element being coupled to a respective wordline; associated to each bit-line is a biasing transistor having a control terminal, and the circuit generates a cascode voltage for this control terminal; a driver stage is coupled to one end of each wordline. The circuit generates the cascode voltage based on a reference voltage, which is a function of the emulation of a voltage drop on the driver stage, on the wordline, and on the memory cell as a result of a current associated to the corresponding selector element.

Bit-line voltage generation circuit for a non-volatile memory device and corresponding method

An embodiment non-volatile memory device includes an array of memory cells, coupled to word lines, and a row decoder including a pull-down stage and a pull-up stage, which includes, for each word line: a corresponding control circuit, which generates a corresponding control signal; and a corresponding pull-up switch circuit, which is controlled via the control signal so as to couple/decouple the word line to/from the supply. The control circuit includes: a current mirror, which injects a current into an internal node; and a series circuit, which couples/decouples the corresponding internal node to/from ground, on the basis of selection/deselection of the corresponding word line so as to cause a decrease/increase in a voltage on the corresponding internal node. Each control signal is a function of the voltage on the corresponding internal node.

Non-volatile memory device including a row decoder with a pull-up stage controlled by a current mirror

A method for programming a phase-change-memory device of a differential type comprises, in a first programming mode, supplying, during a first time interval, a same first programming current, of a type chosen between a SET current and a RESET current, to all the direct and complementary memory cells that are to be programmed with said first programming current; and, in a second programming mode, supplying, during a second time interval, a same second programming current, of the other type chosen between a SET current and a RESET current, to all the direct and complementary memory cells that are to be programmed with said second programming current, thus completing, in just two time steps, writing of a logic word in the memory device.

Method for programming a phase-change memory device of differential type, memory device, and electronic system

In one embodiment, a memory device includes a first sense amplifier, a second sense amplifier, a first lower switch arranged between a first lower main bit line and a first input of the first sense amplifier, a second lower switch arranged between the first lower main bit line and a first input of the second sense amplifier, a first upper switch arranged between a first upper main bit line and the first input of the first sense amplifier, a second upper switch arranged between the first upper main bit line and the first input of the second sense amplifier, a third lower switch arranged between a second lower main bit line to a second input of the first sense amplifier, and a third upper switch arranged between a second upper main bit line to a second input of the second sense amplifier.

Device for switching between different reading modes of a non-volatile memory and method for reading a non-volatile memory

A memory device includes an array of phase-change memory cells and a word line. The memory device includes a control circuit, a first pull-up MOSFET and a second pull-up MOSFET connected in series between a first power-supply node set at a first supply voltage and the word line, a first pull-down MOSFET and a second pull-down MOSFET connected in series between the word line and a second power-supply node set at a reference potential, and a biasing MOSFET connected between the word line and a third power-supply node set at a second supply voltage higher than the first supply voltage. The first and second pull-up MOSFETs and the first and second pull-down MOSFETs have breakdown voltages lower than the breakdown voltage of the biasing MOSFET.

Phase-change memory device with drive circuit

A memory device including a first memory sector and a second memory sector, each of which includes a respective plurality of local bit lines, which may be selectively coupled to a plurality of main bit lines. The memory device further includes a first amplifier and a second amplifier, and a routing circuit, arranged between the main bit lines and the first and second amplifiers. The routing circuit includes: a first lower switch, arranged between a first lower main bit line and a first input of the first amplifier; a second lower switch, arranged between the first lower main bit line and a first input of the second amplifier; a first upper switch, arranged between a first upper main bit line and the first input of the first amplifier; and a second upper switch, arranged between the first upper main bit line and the first input of the second amplifier. The second inputs of the first and second amplifiers are coupled to a second lower main bit line and to a second upper main bit line, respectively.

According to one embodiment, a PCM memory device includes a memory matrix having memory cells of the phase-change type organized in a plurality of word lines and bit lines. Each memory cell has a storage element and an access element including at least one MOS transistor, which is controlled to allow access to the storage element and to carry out read/programming storage operations, in which source terminals of the MOS transistors of access elements of the memory cells of the same word line are connected to the same source line. The source lines of the memory matrix are electrically short-circuited in groups. A single source line driver element for each group of source lines is configured in such a manner as to generate a respective source line driver signal in order to bias in a corresponding manner all the source lines of the respective group.

Phase change memory device with selector MOS transistors and source line clustering

An embodiment memory device includes a memory array having a plurality of bit lines, a low-voltage connection path configured to connect, in an operational phase of the device, an access terminal to a selected local bit line of the plurality of bit lines, and a high-voltage connection path configured to connect, in the operational phase of the device, the access terminal to the selected local bit line, in parallel with the low-voltage connection path.

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