摘要:
In the programming of a non-volatile memory device, such as a NAND flash memory device 100, a positive bias voltage V.sub.bias is applied to a bit line 44 to set a respective memory gate 44a in a programmed state. In a further embodiment, the positive bias voltage V.sub.bias is obtained by dividing the select drain gate voltage V.sub.cc using two resistors 56 and 58 connected in series.
摘要:
A flash memory including a page buffer with bias circuitry and a reference array enabling reading and verifying values stored on a word line of memory cells in parallel using the page buffer irrespective of temperature, Vcc, and process variations. The bias circuitry includes a cascode transistor having a source connected to the reference cell array which provides a single reference signal. The bias cascode couples the reference signal to an input of a bias inverter in the bias generator, while a bias load transistor in the bias generator couples Vcc to the bias inverter input. The page buffer includes a set of latches that are each coupled to a memory cell by a cascode. A first inverter in each latch has transistors with sizes matching the transistors in the bias inverter. A latch load transistor is connected between a pull-up and pull-down transistor of a second inverter in each latch and is sized to match the bias load transistor. Gates of the bias load transistor and the latch load transistor are both coupled to the output of the bias inverter enabling the first inverter of each latch to have an input mirroring the input of the bias inverter.
摘要:
An emulated EEPROM memory array is disclosed based on non-volatile floating gate memory cells, such as Flash cells, where a small group of bits share a common source line and common row lines, so that the small group of bits may be treated as a group during program and erase modes to control the issues of program disturb and effective endurance. The bits common to the shared source line make up the emulated EEPROM page which is the smallest unit that can be erased and reprogrammed, without disturbing other bits. The memory array is physically divided up into groups of columns. One embodiment employs four memory arrays, each consisting of 32 columns and 512 page rows (all four arrays providing a total of 1024 pages with each page having 8 bytes or 64 bits). A global row decoder decodes the major rows and a page row driver and a page source driver enable the individual rows and sources that make up a given array. The page row drivers and page source drivers are decoded by a page row/source supply decoder, based on the addresses to be accessed and the access mode (erase, program or read).
摘要:
Method and apparatus for a memory circuit having a sense amplifier circuit having a sensing amplifier connected to read the data content output of a memory cell where the sense amplifier circuit includes a current source transistor having a gate terminal and having a drain terminal connected to a voltage supply and having a source terminal connected to the sensing amplifier, with a selectable source current in order to account for variation from a desired source current due to variations in the designed source current transistor performance parameters.
摘要:
A decoder for decoding from two sides of a memory array. The decoder is positioned on two sides of the memory array. The decoder includes driver circuits that are connected to routing lines from the memory array. To reduce the size of the decoder, some of the routing lines extend from one side of the memory array and the remaining routing lines extend from the other side of the memory array.
摘要:
A method of erasing a memory cell that has a first region and a second region with a channel therebetween and a gate above the channel, and a charge trapping region that contains an initial amount of charge. The method includes applying a first cycle of voltages across the gate and the first region so that the first amount of charge is removed from the charge trapping region. A second amount of charge is written into the charge trapping region and subsequently a second cycle of one or more voltages is applied across the gate and the first region so that the second amount of charge is removed from the charge trapping region, wherein the initial applied voltage of the second cycle of voltages is equal to the final applied voltage of the first cycle of voltages.
摘要:
The present invention provides a method of verifying that all flash EEPROM transistors in a NAND string are properly erased without overerasing by applying a bias voltage to the source of the bottom select gate of the NAND array and applying a non-negative erase verify voltage to the control gates of each transistor during an erase verify. The bias voltage is at least equal to the erased threshold voltage of the worst case transistor to ensure proper erase verification. If all transistors are not erased, then another erase operation is performed. Erasing is repeated until the erase verify operation indicates that all transistors are properly erased. By erasing and verifying according to the present invention, the NAND array is completely and properly erased while minimizing overerasing the array.
摘要:
An EEPROM NAND array has floating gate memory cells coupled in series, each having a control gate, a floating gate, a body region, and an insulating layer between the floating gate and the body region. A negative charge pump is coupled to the body region. In programming, the body region of the memory cell selected for programming is biased to a negative voltage by the negative charge pump while the control gate of the memory cell is biased to a predetermined positive voltage sufficient to induce Fowler-Nordheim tunneling from the body region into the floating gate. The present invention allows the programming voltage requirement at the control gate of a NAND EEPROM memory cell to be significantly reduced which allows for the peripheral voltage delivery circuitry in NAND EEPROM arrays to be designed for lower voltages than for conventional NAND EEPROM arrays.
摘要:
A non-volatile memory device includes a plurality of MOS transistors 34 and 36 connected to respective word lines 16 and 18 to allow individual pages of memory stored in the memory cells 8a, 10a and 8b, 10b on the respective word lines 16 and 18 to be erased and erase verified. A method of erasing a page of memory cells includes the steps of applying an erase voltage to one of the MOS transistors 16 and 18 to erase the page of memory cells along the respective word line, and applying an initial erase-inhibit floating voltage to other MOS transistors which are connected to the word lines unselected for page erase. In an erase verify mode, an erase verify voltage is applied to the word line which was selected for page erase in the erase mode, and an erase verify unselect voltage is applied to the word lines which was not selected for page erase.
摘要:
A programmable reference used to identify a state of an array cell in a multi-density or low voltage supply flash EEPROM memory array. The programmable reference includes one or more reference cells, each reference cell having a floating gate which is programmed to control its threshold value. The array cells are read by applying an identical voltage to the gate of the array cell and the reference cell and comparing outputs to determine the array cell state. During read of an array cell, the programmable reference cell is biased the same as the array cell, so that the difference in threshold values between reference cells and array cells remain constant with a change in V.sub.CC. Circuitry is included for programming the reference cells utilizing a simple resistor ratio. Programming is performed at test time, preferably by the manufacturer, to assure V.sub.CC remains within strict tolerances. The array cells are programmed and read without resistor biasing and under looser tolerances using the reference cells at a later time.