Texas Instruments Corporation

Sung-Wei Lin

Manzur Gill

Tim M Coffman

Phat C Truong

Sebastiano D'Arrigo

David J McElroy

Sudhir Kumar Madan

T Damodar Reddy

Dennis R Robinson

John Y Fong

Ronald J Syzdek

Anand Seshadri

C Rinn Cleavelin

Jarrod Eliason

Giuliano Imondi

Inn K Lee

Timothy J Coots

Iano D'Arrigo

John Frederic Schreck

Hugh Pryor McAdams

Benjamin H Ashmore, Jr

Stephen Keith Heinrich-Barna

Harvey J Stiegler

Gill Manzur

Hugh P Mcadams

Ming-Bo Liu

One embodiment of the invention includes a memory system. The system comprises a memory cell coupled to a bit-line node. The memory cell can be configured to generate a bit-line current on the bit-line node in response to a bias voltage during a read operation. The system further comprises a sense amplifier configured to maintain a substantially constant voltage magnitude of the bit-line node during a pre-charge phase and a sense phase of the read operation based on regulating current flow to and from the bit-line node, and to determine a memory value of the flash memory transistor during the read operation based on a magnitude of the bit-line current on the bit-line node.

System and method for reading memory

One aspect of the invention relates to a method for accessing a memory device. One embodiment relates to a method for accessing a memory device. In the method during a read operation, one data value is provided on a local IO line while complimentary local IO line that is associated with the local IO line is inactivated. During a write operation, another data value is provided on the local IO line and a complimentary data value is provided on the complimentary local IO line. Other systems and methods are also disclosed.

Methods and systems for accessing memory

Methods are described for operating a FeRAM and other such memory devices in a manner that avoids over-voltage breakdown of the gate oxide in memory cells along dummy bit lines used at the edges of memory arrays, the methods comprising floating the dummy bit line during plate line pulsing activity. In one implementation of the present invention the method is applied to a FeRAM dummy cell having a plate line, a dummy bit line, a pass transistor, and a ferroelectric storage capacitor. The method comprises initially grounding the dummy bit line as a preferred pre-condition, however, this step may be considered an optional step if the storage node of the storage capacitor is otherwise grounded. The method then comprises floating the dummy bit line, activating a word line associated with the memory cell, and pulsing the plate line. Alternately, the method comprises applying a positive voltage bias to the dummy bit line in place of, or before floating the dummy bit line. The method may further optionally comprise grounding the dummy bit line after pulsing the plate line, and optionally disabling the word line after grounding the dummy bit line to precondition the cell for the next memory operation.

Active float for the dummy bit lines in FeRAM

An FeRAM memory array wherein the plate lines run in the direction of word lines is described that provides a reduced plate line resistance in arrays having a common plate line connection. The lower plate line resistance reduces the magnitude of negative spikes on the plate line to reduce the potential for FeCap depolarization. Two or more plate lines of a plurality of columns of memory cells are interconnected along a bit line direction. Some or all of the plate lines of one or more columns of dummy memory cells may also be interconnected to reduce the plate line resistance and minimize any increase in the bit line capacitance for the active cells of the array. The improved FeRAM array provides a reduced data error rate, particularly at fast memory cycle times.

Low resistance plate line bus architecture

A memory circuit and method to reduce wordline coupling is disclosed. The circuit includes a plurality of memory cells arranged in rows (, and) and columns (). A first conductor () is coupled to a plurality of the rows (, and) of memory cells. A first transistor () has a current path coupled between a voltage supply terminal () and the first conductor () and a control terminal coupled to receive a first control signal (PLV). A second transistor () has a current path coupled between the voltage supply terminal and the first conductor and a control terminal coupled to receive a second control signal (PLW).

Plateline driver with RAMP rate control

Systems and methods fatigue a ferroelectric memory device. Within a single cycle, a group of selected ferroelectric memory cells is fatigued by reading a first logical value from the cells while also writing a second logical value to the memory cells. The first logical value is temporarily stored into latches of sense amplifiers associated with the selected memory cells in order to decipher logical values. Subsequently, the first logical value is written back to the ferroelectric memory cells and a cycle of the fatigue operation is ended.

Accelerated low power fatigue testing of FRAM

Methods and ferroelectric devices are presented, in which pulses are selectively applied to ferroelectric memory cell wordlines to discharge cell storage node disturbances while the cell plateline and the associated bitline are held at substantially the same voltage.

Method and apparatus to reduce storage node disturbance in ferroelectric memory

A supply-voltage detecting stage (11) that supplies first and second reference currents (I.sub.REFP and I.sub.REFN) which vary with the supply voltage (V.sub.cc) and are coupled by first and second gain stages (12A and 12B), respectively, to first and second temperature-detecting stages (13A and 13B), respectively. First and second temperature-detecting stages (13A and 13B) increase the coupled reference currents (I.sub.REFP and I.sub.REFN), respectively, to compensate for temperature increase through use temperature-sensitive, long-channel transistors (M34-M37 and M42-M45), supplying temperature and supply-voltage compensated output bias voltages at output terminals (MIRN and MIRP).

Temperature and supply-voltage sensing circuit

The method of this invention prevents transient currents at high-frequency disable cycles and disables DC current paths after a minimum delay time, thereby reducing power dissipation. This invention includes a delay circuit functioning to prevent disablement of DC paths where chip-disable times occur at intervals below a minimum duration. The result is a decrease in the number of undesired voltage drops on internal power buses due to transient currents. The method detects external chip-disable pulses that occur before a minimum time duration, then prevents those pulses from powering down internal direct-current paths. At the same time, the output driver high impedance functionality of the chip-disable signal is preserved.

Memory device performance by delayed power-down

In a multi-sector nonvolatile memory array in which each memory cell has a drain coupled to a bitline, each memory cell of each sector has a source coupled to a common array-source line, each memory cell in a row of the first sector has a control gate coupled to a wordline and each memory cell of a row in another sector has a control gate coupled to that wordline, a method for programming a memory cell in one sector of said method includes connecting at least the second common array-source line to each bitline coupled to drains of columns of memory cells in the another sector, then biasing at a positive voltage both the common array-source line and the bitlines coupled to drains of memory cells in columns of the another sector, and then applying a programming voltage to the selected wordline coupled to the control gate of the selected cell in the first sector. An erasing method includes connecting the wordlines to a reference voltage, connecting at least one deselected common array-source line to each bitline coupled to drains of columns of memory cells in the deselected sector, then biasing at a positive voltage both the deselected common array-source line and said bitlines coupled to drains of memory cells in columns of the deselected sector, and then applying a positive erasing voltage to said common array-source line of the selected sector.

Array-source line, bitline and wordline sequence in flash operations

The circuit of this invention improves significantly the programming speed of a Flash EPROM. The circuit includes a detector circuit (DC) using a pre-charge capacitor (C1), capacitor dividers [(C1/(C1+C2) and C3/(C2+C3)] and a voltage comparator (COMP) to signal a control logic circuit (CLC) when the programming voltage is within supply voltage (V.sub.cc) of its final value. At that point the control logic circuit (CLC) boosts the voltage on one terminal of a boost capacitor (BC) by the value of the supply voltage (V.sub.cc). The other terminal (XDD) of the boost capacitor (BC) furnishes the boosted programming voltage for the Flash EPROM.

Smart boost circuit for low voltage flash EPROM

A procedure for erasing a Flash EPROM array (AR) includes applying a series of erase pulses to all of the subarrays (S1, S2, etc.) of a Flash EPROM array (AR) simultaneously. Between each erase pulse, the memory cells (10) of each sub array (S1, S2, etc.) are simultaneously checked one row at a time and one column position at a time, to see whether or not any cell (10) is over-erased. If, at any time during the procedure a cell (10) is found to be over-erased, the over-erased condition is corrected and the erase procedure continues, but with erase pulses applied only to those subarrays (S1, S2, etc.) having non-erased memory cells (10) as in prior-art subarray erase procedures. Under almost all circumstances, the procedure of this invention decreases over-all erase time.

Erase procedure

An electrically-erasable, electrically-programmable, read-only-memory cell array is formed in pairs at a face of a semiconductor substrate (22). Each memory cell includes a source region (11) and a drain region (12), with a corresponding channel region between. A Fowler-Nordheim tunnel-window (13a) is located over the source line (17) connected to source (11). A floating gate (13) includes a tunnel-window section. A control gate (14) is disposed over the floating gate (13), insulated by an intervening inter-level dielectric (27). The floating gate (13) and the control gate (14) include a channel section (Ch). The channel section (Ch) is used as a self-alignment implant mask for the source (11) and drain (12) regions, such that the channel-junction edges are aligned with the corresponding edges of the channel section (Ch). The memory cell is programmed by hot-carrier injection from the channel to the floating gate (13), and erased by Fowler-Nordheim tunneling from the floating gate (13) through the tunnel window (13a) to the source-line (17 ). The program and erase regions of the cells are physically separate from each other, and the characteristics, including the oxides, of each of those regions may be made optimum independently from each other.

Method of making an EEPROM cell with separate erasing and programming

A method for erasing blocks of a non-volatile memory includes detecting whether a block is in at least one of an erased state or a state secured from erasure; then setting a flag register at a first level for each block detected to be in at least one of an erased state or a state secured from erasure or at a second level for each block not so detected; then selecting for erasure blocks that have their respective flags set at the second level; and then erasing the selected blocks.

Smart erase algorithm with secure scheme for flash EPROMs

The power-on-reset test circuit of this invention includes two imbalanced latches to detect the occurrence of a transient power-on-reset signal. The occurrence of a transient power-on-reset signal is latched for later verification during circuit testing. Both latches are designed to default to a low voltage output (Vss) on initial power-up. One of the latches is set by the power-on-reset signal to a high-voltage output (Vcc) state. The other latch is set by a reference-potential input to a low-voltage output state. If the set latch has a high-voltage output and the other latch has a low-voltage output, then the power-on-reset circuitry is functioning properly.

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Houston, TX, United States of America

Sung-Wei Lin