摘要:
A sensing circuit for serial dichotomic sensing of multiple-level memory cells which can take one programming level among a plurality of m=2.sup.n (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. The variable reference current generator comprises an offset current generator permanently coupled to the current comparator, and m-2 distinct current generators, independently activatable by the successive approximation register, each one generating a current equal to a respective one of the plurality of cell current values.
摘要:
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. The variable reference current generator comprises an offset current generator permanently coupled to the current comparator, and m−2 distinct current generators, independently activatable by the successive approximation register, each one generating a current equal to a respective one of the plurality of cell current values.
摘要:
Reading circuit for multilevel non-volatile memory cell devices having, for each cell to be read, a selection line with which is associated a load and a decoupling and control stage with a feedback loop which stabilizes the voltage on a circuit node of the selection line. To this node are connected a current replica circuit which are controlled by the feedback loop. These include loads and circuit elements homologous to those associated with the selection line of the memory cell and have an output interface circuit for connection to current comparator circuit.
摘要:
A method for sensing multiple-levels non-volatile memory cells which can take one programming level among a plurality of m=2.sup.n (n>=Z) different programming levels, provides 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 discrete set of m distinct cell current values, each cell current value corresponding to one of said programming levels. The sensing method also provides for: simultaneously comparing the cell current with a prescribed number of reference currents having values comprised between a minimum value and a maximum value of said discrete set of m cell current values and dividing said discrete set of m cell current values in a plurality of sub-sets of cell current values, for determining the sub-set of cell current values to which the cell current belongs; repeating step (a) for the sub-set of cell current values to which the cell current belongs, until the sub-set of cell current values to which the cell current belongs comprises only one cell current value, which is the value of the current of the memory cell to be sensed.
摘要:
A device for reading memory cells, wherein the device contains two branches, wherein each branch comprises, connected in cascade, an electronic switch, an active element reactively connected to the active element of the other branch, so as to form a voltage amplifier. Each active element is controlled by means of a high impedance circuit element. A microswitch connects the two branches together is inserted between the two active elements.
摘要:
A timing circuit for reading from a device comprising multi-level non-volatile memory cells, which circuit comprises a single programmable delay block connected to an input terminal for memory address line transition signals. The delay block drives a counter which feedback controls the discharge through a combinational logic circuit connected to the output terminal of the programmable delay block. A logic output circuit, connected to the output terminal of the delay block and to the counter, generates the timing signals.
摘要:
A nonvolatile memory apparatus includes a separate controller circuit and memory circuit. The controller circuit is fabricated on a first integrated circuit chip. The controller circuit includes a plurality of charge pump circuits, a system interface logic circuit, a memory control logic circuit, and one or more analog circuits. The memory circuit is fabricated on a second integrated circuit chip and includes a column decoder, a row decoder, a control register, and a data register. A memory-controller interface area includes a first plurality of die bond pads on the first integrated circuit chip and a second plurality of die bond pads on the second integrated circuit chip such that the first and second integrated circuit chips may be die-bonded together. A single controller circuit may interface with a plurality of memory circuits, thus further reducing overall costs as each memory circuit does not require a dedicated controller circuit.
摘要:
A voltage regulator for supplying two types of loads on a common chip, namely a high current load and a low current load. The voltage regulator employs a feedback loop to supply the low current load with a fine degree of regulation and a feed forward arrangement to supply the high current load with a coarse degree of regulation. The feedback loop employs a bandgap reference source feeding a comparator, with an output driver transistor drawing current from a common supply and having an output electrode connected to a voltage divider, allowing a sample of the output to be fed back to the comparator to maintain the desired output voltage. The output electrode also feeds a control transistor for the feed forward arrangement that also draws current from the common supply and supplies the high current load directly. An example of a single chip circuit employing the present invention is a charge pump where the high current load is a series of large capacitors used to multiply charge to produce a high voltage and the low current load is a plurality of clock circuits that apply timing pulses to switches for proper phasing of the capacitors and associated switches to achieve the desired high voltage.
摘要:
Column redundancy is provided outside of a FLASH memory chip using a separate companion controller chip. The companion chip initially receives and stores fuse address information from the FLASH memory chip for defective memory cells in the FLASH memory. In a read mode of operation, the companion control chip detects receipt of a defective address from the FLASH memory and stores in a redundant shift register redundant data that is downloaded from the FLASH memory chip. The redundant data is used to provide correct FLASH memory data to an external user that interfaces with the companion control chip. In a program mode of operation, the companion control chip provides redundant bits that are stored in redundant columns in the FLASH memory chip. The companion control chip provides flexibility by readily providing a number of different redundancy schemes for bits, nibbles, or bytes without requiring additional logic circuits in the FLASH memory chip itself. Data is transferred between the FLASH memory chip and the companion control chip a byte at a time.
摘要:
The present invention is related to semiconductor memories, and in particular, to a nonvolatile or flash memory and method that reduces the effect of or is tolerant of over-erased memory cells. When a memory cell is read, a read voltage is applied to at least one target memory cell, and a negative bias voltage that is lower than a threshold voltage of an over-erased memory cell is also applied to at least one other selected memory cell that is in the same row as the target memory cell. Applying a negative bias voltage to adjacent or proximate memory cells shuts off nearby cells to isolate current that may come from over-erased memory cells during a read, program, or erase operation.