Stmicroelectronics S.r.l.

Stefano Commodaro

Giovanni Campardo

Rino Micheloni

Marco MacCarrone

Andrea Ghilardelli

Jacopo Mulatti

Massimiliano Picca

Maurizio Branchetti

Stefano Ghezzi

Matteo Zammattio

Guido Lomazzi

Patrizia Mongelli

Francesco Farina

Marcelo Carrera

A method and control device is used for testing electronic memory devices. The method comprises loading test data and/or instructions into a control logic circuit portion associated with a matrix array of memory cells and integrated storage circuitry. According to the invention, a test operation control device is used temporarily instead of the control logic, the test operation control device being external of and connected detachably to the memory device. Advantageously, the test operation control device is a matrix cell array external of the memory.

Method and a device for testing electronic memory devices

The memory array comprises a plurality of cells, grouped together in sectors and arranged in sector rows and columns, and has both hierarchical row decoding and hierarchical column decoding. Global word lines are connected to at least two word lines in each sector, through local row decoders; global bit lines are connected to at least two local bit lines in each sector, through local column decoders. The global column decoder is arranged in the center of the memory array, and separates from each other an upper half and a lower half of the memory array. Sense amplifiers are also arranged in the middle of the array, thus saving space. This architecture also provides lesser stress of the cells, better reliability, and better production performance. In addition, each sector is completely disconnected from the remaining sectors, and only the faulty row or column of a single sector should be doubled.

Nonvolatile memory device, in particular a flash-EEPROM

Circuit for discharging to ground, supplied by a supply voltage, comprising a reference voltage, a negative potential node, first circuitry adapted to couple the negative potential node to the reference voltage in response to a control signal. Second circuitry is provided adapted to determine in the first circuitry the passage of a controlled current for the discharge of the negative potential node.

Circuit for discharging a negative potential node to ground, including control of the discharge current

A method and related circuit for adjusting the duration of a pulse synchronization signal for the reading phase of memory cells in electronic memory devices which are integrated on semiconductors are discussed. The pulse synchronization signal is produced by a pulse generator when it detects a logical state commutation on at least one input terminal of a plurality of addressing input terminals of the memory cells. The method produces a logical sum between the signal produced by the generator and a pulse signal having a predetermined duration. The logical sum is used to start up the reading phase.

Method and a related circuit for adjusting the duration of a synchronization signal ATD for timing the access to a non-volatile memory

An electronic circuit generates a stable voltage signal for the polarization during a reading step of a UPROM redundancy cell incorporating at least one memory element of EPROM or Flash type, having at least one terminal to be polarized, and MOS transistors which connect such memory element to a low voltage power supply reference. The circuit includes a current mirror structure with a first control branch and a second output branch. The current mirror stricture includes a first series of MOS transistors (M,, M,, M,) in said first branch between the supply reference and a ground; and a second series of transistors (M,, M,, M,) in said second branch. The circuit also includes an input terminal connected to the gate terminal of a transistor of the first series of transistors and an output terminal corresponding to an interconnection node of the second series of transistors. The stable voltage is obtained through a current which passes through at least a pair of transistors of the second series.

Electronic circuit for generating a stable voltage signal for polarizing during a reading step UPROM memory cells operating at low feed voltage

The read circuit has an array branch connected to an array cell, and a reference branch connected to a reference cell; the array branch presents an array load transistor interposed between a supply line and the array cell, and the reference branch presents a reference load transistor interposed between the supply line and the reference cell; and the array and reference load transistors form a current mirror wherein the array load transistor is diode-connected and presents a first predetermined channel width/length ratio, and the reference load transistor presents a second predetermined channel width/length ratio N times greater than the first ratio, so that the current flowing in the array cell is supplied, amplified, to the reference branch.

Method and circuit for reading low-supply-voltage nonvolatile memory

Switching circuit that receives a supply voltage, a reference voltage, a line adapted to carry a negative voltage and a control signal, the switching circuit capable of providing at an output a voltage alternatively equal to the reference voltage or to the voltage of the line in response to the control signal. The circuit includes a first MOSFET with a first electrode operationally connected to the line, a second electrode operationally connected to the output, and a control electrode, a second MOSFET with a first electrode operationally connected to the reference voltage, a second electrode operationally connected to the output, and a control electrode, and driving circuitry adapted to bring the control electrodes of the first and second MOSFETs respectively to the supply voltage and to the voltage of the line or, alternatively, to the voltage of the line and to the supply voltage, in response to the control signal.

Switching circuit having an output voltage varying between a reference

The row decoder includes a predecoding stage supplied with row addresses and generating predecoding signals; and a final decoding stage, which, on the basis of the predecoding signals, drives the individual rows in the array. The predecoding stage includes a number of predecoding circuits presenting two parallel signal paths: a low-voltage path used in read mode, and a high-voltage path used in programming mode. A CMOS switch separates the two paths, is driven by high voltage via a voltage shifter in programming mode, and, being formed at predecoding level, involves no integration problems.

Line decoder for memory devices

A band-gap reference voltage generator comprises an operational amplifier comprising a first input and a second input, the first input being coupled to a first feedback network and the second input being coupled to a second feedback network both coupled to an output of the operational amplifier providing a reference voltage. The first feedback network contains an emitter-base junction of first bipolar junction transistor and the second feedback network contains an emitter-base junction of second bipolar junction transistor. A selectively activated current supply supplies a bias current to the operational amplifier, the current supply being deactivatable in a substantially zero power consumption operating condition for turning the reference voltage generator off. A start-up circuit activated upon start-up of the reference voltage generator for a fixed, prescribed time interval forces a start-up current to flow through the first bipolar junction transistor means.

Band-gap reference voltage generator

A nonvolatile memory having a memory array including a plurality of data cells and a read circuit. The read circuit includes a plurality of sense amplifiers, each connected to a respective array branch to be connected to the data cells. The nonvolatile memory also includes a reference generating circuit including a single reference cell arranged outside the memory array and generates a reference signal. The reference generating circuit includes a plurality of reference branches, each connected to a respective sense amplifier, and circuits interposed between the reference cell and the reference branches to supply the reference branches with a signal based on the reference signal.

Single-cell reference signal generating circuit for reading nonvolatile

The memory device has a plurality of local boost circuits, each connected to a sector of the memory array, and each having a control circuit, at least a respective boost capacitor, and a respective drive circuit. Each drive circuit is only enabled in read mode, on receiving an address-transition-detect signal and a sector enabling signal, for reading memory cells forming part of the respective sector. The boost voltage is only supplied to the final inverter of the row decoder. A clamping diode limits the boost voltage to prevent undesired direct biasing of the PMOS transistors of the final inverters connected to the nonaddressed word lines. And the overvoltage is therefore only supplied locally when and where necessary.

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Bogliasco, Italy

Stefano Commodaro