Abstract: An asymmetric switch which minimizes transistor exposure to high voltage includes one pair of P-channel transistors with both N-wells coupled back to the programming voltage source and one pair of P-channel transistors with independent N-wells. Two pairs of N-channel transistors and an inverting circuit are also included to provide complementary input voltages to the switch. The P-channel and N-channel transistors used as guard devices may be biased by the same voltage or separate voltages.

Abstract: First and second flash memory cells or transistors, operating in the linear region of operation, are provided with different threshold values by providing different charges on their respective floating gates. The first of the pair of flash memory transistors is "over-erased" until it has a negative threshold voltage so that the first flash memory transistor is rendered permanently conducting when its control gate and source are at V.sub.ss. Circuitry is provided for connecting the first and second flash memory transistors in parallel circuits in which equal current values are generated in an equilibrium condition. Circuitry for sensing a voltage in each of the parallel circuits is provided to determine any imbalance in current values and provide an output voltage which may be used as an reference value when the currents are in equilibrium.

Abstract: An operational amplifier-based voltage multiplier circuit ("op amp circuit") implemented as an integrated circuit, and a memory chip including such an op amp circuit. The op amp circuit includes a variable operational feedback or input resistance (or a variable operational feedback resistance and a variable input resistance), and preferably also circuitry for controlling at least one variable resistance in response to control bits to cause the op amp circuit to assert a selected output voltage in response to a given input voltage. Preferably, each set of control bits determines a binary control word whose binary value has a simple functional relation to the value of the output voltage selected thereby. Preferably, the memory chip includes an array of memory cells (e.g, flash memory cells) and a control unit for controlling memory operations including programming, reading, and erasing the memory cells.

Abstract: An integrated circuit operable in a test mode and a normal operating mode, which includes an improved test mode switch. In the test mode of preferred embodiments in which the circuit is an integrated memory chip, the test mode switch is closed so as to connect an input/output (I/O) pad directly with a selected memory cell (so a current/voltage characterization of the cell can be obtained). In the normal operating mode of these embodiments, the test mode switch is open and it isolates the I/O pad from direct connection with the selected cell even under the condition that a transistor of the test mode switch undesirably becomes conductive (e.g., due to low voltage on the I/O pad, inductive coupling, or the like).

Abstract: A flash memory array having a reduced number of metal source lines and increased storage density. The cells are arranged in rows and columns, with the cells in a row having their control gates connected to a common word line and the cells in a column having their drains connected to a common bit line. All of the cell sources of the array are connected together with a combination of doped semiconductor and metal lines. The source metal lines are disposed generally in parallel with the bit lines. In order to reduce the number of source metal lines, the lines are spaced apart by, typically, eight, sixteen or more cell columns. The metal source lines define a sub-array therebetween. The array includes a decoder for accessing two cells in different columns of each sub-array during single reading and programming operations. Thus, each sub-array provides two bits of data rather than the customary one bit.

Abstract: An asymmetric switch which minimizes transistor exposure to high voltage includes one pair of P-channel transistors with both N-wells coupled back to the programming voltage source and one pair of P-channel transistors with independent N-wells. Two pairs of N-channel transistors and an inverting circuit are also included to provide complementary input voltages to the switch. The P-channel and N-channel transistors used as guard devices may be biased by the same voltage or separate voltages.

Abstract: A non-volatile data storage unit having a data input and a volatile memory device for storing data. The volatile memory device is preferably a latch circuit made up of a pair of cross-coupled inverter circuits which store the data in complementary form. A non-volatile memory device, such as a pair of flash memory cells, is included which also store data in complementary form. Control circuitry is provided for controlling the operation of the data storage unit, including circuitry for transferring data from the data input to the volatile memory device and circuitry for programming the non-volatile memory device with data from the volatile memory device. The storage unit also preferably includes circuitry for transferring data stored in the non-volatile memory device to the volatile memory device, with such transfer typically taking place after an interruption of power to the storage unit.

Abstract: A fast-sensing amplifier for a flash memory comprised of a plurality of floating-gate memory devices and having a column line selectively coupled to the devices is disclosed. The column line is quickly discharged to ground before a read-biasing and amplifying circuit quickly pulls up the line to the read-bias potential at a particular memory device. This potential is compared to a sense-reference potential by a differential amplifier within the fast-sensing amplifier. The binary state of the particular memory device is provided as the output of the fast-sensing amplifier.

Abstract: A fast-sensing amplifier for a flash memory comprised of a plurality of floating-gate memory devices and having a column line selectively coupled to the devices is disclosed. The column line is quickly discharged to ground before a read-biasing and amplifying circuit quickly pulls up the line to the read-bias potential at a particular memory device. This potential is compared to a sense-reference potential by a differential amplifier within the fast-sensing amplifier. The binary state of the particular memory device is provided as the output of the fast-sensing amplifier.

Abstract: A memory system capable of being configured for optimum performance after fabrication using control parameters stored in non-volatile data storage units. The system includes an array of memory cells, separate from the data storage units, arranged in a multiplicity of rows and a multiplicity of columns, with each cell located in one of the rows being coupled to a common word line and with each cell located in one of the columns being coupled to a common bit line. Control circuitry for controlling memory operations such as programming the memory cells and reading the memory cells when the memory system is in a normal mode of operation. The non-volatile data storage units store control parameter data used by the control means for controlling the memory operations, with the control parameters being modifiable when the memory system is placed in an alternative mode of operation as opposed the normal mode of operation.

Abstract: A level detection circuit for monitoring the level of a power supply voltage and producing an output signal at power on for resetting various system elements powered by the supply voltage when the supply voltage reaches a predetermined level. The detection circuit, which is powered by the supply voltage includes a voltage reference circuit which produces a reference voltage having a magnitude which is relatively independent of the power supply voltage. A translator circuit functions to produce a translated voltage indicative of the supply voltage magnitude and which is comparable in magnitude to the reference voltage when the supply voltage is at a suitable level such that the system will accept a power on reset pulse. A comparator circuit functions to compare the reference voltage with the translated voltage and cause an associated output circuit to issue the reset pulse. The reset circuit typically includes a one shot circuit, the output of which is logically ORed with the amplified comparator output.

Abstract: A fast-sensing amplifier for a flash memory comprised of a plurality of floating-gate memory devices and having a column line selectively coupled to the devices is disclosed. The column line is quickly discharged to ground before a read-biasing and amplifying circuit quickly pulls up the line to the read-bias potential at a particular memory device. This potential is compared to a sense-reference potential by a differential amplifier within the fast-sensing amplifier. The binary state of the particular memory device is provided as the output of the fast-sensing amplifier.

Abstract: First and second flash memory cells or transistors, operating in the linear region of operation, are provided with different threshold values by providing different charges on their respective floating gates. The first of the pair of flash memory transistors is "over-erased" until it has a negative threshold voltage so that the first flash memory transistor is rendered permanently conducting when its control gate and source are at V.sub.ss. Circuitry is provided for connecting the first and second flash memory transistors in parallel circuits in which equal current values are generated in an equilibrium condition. Circuitry for sensing a voltage in each of the parallel circuits is provided to determine any imbalance in current values and provide an output voltage which may be used as an reference value when the currents are in equilibrium.

Abstract: An integrated circuit operable in a test mode and a normal operating mode, which includes an improved test mode switch. In the test mode of preferred embodiments in which the circuit is an integrated memory chip, the test mode switch is closed so as to connect an input/output (I/O) pad directly with a selected memory cell (so a current/voltage characterization of the cell can be obtained). In the normal operating mode of these embodiments, the test mode switch is open and it isolates the I/O pad from direct connection with the selected cell even under the condition that a transistor of the test mode switch undesirably becomes conductive (e.g., due to low voltage on the I/O pad, inductive coupling, or the like).

Abstract: An operational amplifier-based voltage multiplier circuit ("op amp circuit") implemented as an integrated circuit, and a memory chip including such an op amp circuit. The op amp circuit includes a variable operational feedback or input resistance (or a variable operational feedback resistance and a variable input resistance), and preferably also circuitry for controlling at least one variable resistance in response to control bits to cause the op amp circuit to assert a selected output voltage in response to a given input voltage. Preferably, each set of control bits determines a binary control word whose binary value has a simple functional relation to the value of the output voltage selected thereby. Preferably, the memory chip includes an array of memory cells (e.g, flash memory cells) and a control unit for controlling memory operations including programming, reading, and erasing the memory cells.

Abstract: A non-volatile data storage unit having a data input and a volatile memory device for storing data. The volatile memory device is preferably a latch circuit made up of a pair of cross-coupled inverter circuits which store the data in complementary form. A non-volatile memory device, such as a pair of flash memory cells, is included which also store data in complementary form. Control circuitry is provided for controlling the operation of the data storage unit, including circuitry for transferring data from the data input to the volatile memory device and circuitry for programming the non-volatile memory device with data from the volatile memory device. The storage unit also preferably includes circuitry for transferring data stored in the non-volatile memory device to the volatile memory device, with such transfer typically taking place after an interruption of power to the storage unit.

Abstract: A method for verifying the status of selected nonvolatile memory cells of an integrated memory circuit, such as during a memory erase or programming operation, and an integrated nonvolatile memory circuit including circuitry for performing this verification method. Preferably, the invention employs simple logic circuitry including a flip-flop to assert successful verification data only in response to a continuous validity of a verification signal throughout a sampling period, thereby avoiding false assertion of successful verification data. The sampling period is preferably longer than the expected duration of fluctuations due to noise in the verification signal. During the sampling period of a verification operation, the logic circuitry receives a raw verification signal indicative of the instantaneous relation between a measured threshold voltage of a selected memory cell and a reference voltage.

Abstract: A flash memory array having a reduced number of metal source lines and increased storage density. The cells are arranged in rows and columns, with the cells in a row having their control gates connected to a common word line and the cells in a column having their drains connected to a common bit line. All of the cell sources of the array are connected together with a combination of doped semiconductor and metal lines. The source metal lines are disposed generally in parallel with the bit lines. In order to reduce the number of source metal lines, the lines are spaced apart by, typically, eight, sixteen or more cell columns. The metal source lines define a sub-array therebetween. The array includes a decoder for accessing two cells in different columns of each sub-array during single reading and programming operations. Thus, each sub-array provides two bits of data rather than the customary one bit.

Abstract: An asymmetric switch which minimizes transistor exposure to high voltage includes one pair of P-channel transistors with both N-wells coupled back to the programming voltage source and one, pair of P-channel transistors with independent N-wells. Two pairs of N-channel transistors and an inverting circuit are also included to provide complementary input voltages to the switch. The P-channel and N-channel transistors used as guard devices may be biased by the same voltage or separate voltages.

Abstract: An integrated circuit operable in a test mode and a normal operating mode, which includes an improved test mode switch. In the test mode of preferred embodiments in which the circuit is an integrated memory chip, the test mode switch is closed so as to connect an input/output (I/O) pad directly with a selected memory cell (so a current/voltage characterization of the cell can be obtained). In the normal operating mode of these embodiments, the test mode switch is open and it isolates the I/O pad from direct connection with the selected cell even under the condition that a transistor of the test mode switch undesirably becomes conductive (e.g., due to low voltage on the I/O pad, inductive coupling, or the like).