Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By amplitude
Reexamination Certificate
1999-06-29
2001-02-06
Kim, Jung Ho (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By amplitude
C327S307000, C327S094000, C365S189110
Reexamination Certificate
active
06184726
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of information storage and retrieval using integrated circuit technology. More specifically, the present invention relates to techniques for storing (and retrieving) analog or digital data, or both, within an integrated circuit using multilevel nonvolatile cells.
Among the most important and pioneering innovations in history are devices, techniques, and mediums that have been devised to record and playback sights, sounds, actions, and other information. Many of these innovations have led to the rise and growth of the media and entertainment industries, and also the personal and consumer electronics industries.
For example, among the most notable inventions are Thomas Alva Edison's phonograph and record with which Edison recorded and played his first recording “Mary Had a Little Lamb.” Other achievements in this field are the audio tape recorder, cassette tape recorder, motion picture, talking motion picture (“talkies”), video cassette recorder (VCR), compact disc (CD and CD-ROM), video disc, digital video disc (DVD), and many, many more of such innovations. In the present day, full-length motion pictures with stereo sound may be contained on a single optical disk.
Although these technologies have met with substantial success, there is a continuing desire to improve on the techniques, devices, mediums used to record information. For example, there is a need to provide techniques that provide dense storage of information. Denser storage facilitates storing information in a compact area, and provides a relatively long recording time.
There is a need to provide reliable and robust techniques. The stored reproduction should be a faithful reproduction of the original information. Despite repeated use, the stored reproduction should retain its original form, and also not degrade over time. Furthermore, the techniques should be compatible with and interface easily with present and emerging technologies in electronics and with devices facilitating electronic commerce (such as the Internet and World Wide Web).
Integrated circuit technology has been used to implement many electronic devices including computers, video recorders, digital cameras, microprocessors, DRAMs, SRAMs, Flash memory, and many others. As integrated technology continues to improve, it becomes practical to use this technology to record and playback sights, sounds, actions, and other information.
Data has typically been stored within integrated circuits using a digital or binary format. For applications where the input is analog, however, this requires conversion of signals to digital format, generally by an analog-to-digital (A/D) converter or similar means. And playback of analog signal from a digital storage format may require a digital-to-analog (D/A) converter or similar means. As can be appreciated, these conversions add complexity and extra expense to the entire procedure. Further, a conversion of the signal to digital form quantizes the signal and will lead to quantization noise in the reproduced signal.
Information such as sounds and voices, stereo and multichannel sounds, pictures, video, and others requires many bits of data storage. Storage of data in digital format may be inefficient because one bit (i.e., two different levels) of data is stored in a single memory cell. Further, it may be desirable to store an input signal using a sampling rate the user selects.
Therefore, techniques are needed for compactly storing (and retrieving) analog and digital information including sights, sounds, and actions using integrated circuit technology.
SUMMARY OF THE INVENTION
The present invention provides techniques for storing and retrieving analog or digital information from memory cells. In a specific embodiment, the memory cells are nonvolatile cells capable of analog or multilevel storage. Analog data and analog voltage levels are stored in the cells directly without the need for a conversion to digital form. Analog data is stored by altering a threshold voltage (VT) level of a memory cell to have a unique value representative of the analog data. A memory cell can also be used to store digital data. One or more digital bits can be stored in a single memory cell using a scheme consistent with the analog data storage.
Various different voltage levels are used to configure the memory cells. These voltage levels include high voltages, some of which may be at a level above the highest supply voltage for the integrated circuit. Some of these programming voltages are generated by a charge pump. These voltages are also shifted to a desired voltage level as needed to configure the memory cell to have a particular stored VT representative of the input data. The precision with which these programming voltages is obtained is important. Precise programming voltages are needed to ensure the memory cells are properly written, enhance the reliability and service life of the memory cells, and improve the yield of good die.
Level shifter circuits of the present invention are used to generate an output voltage that is above the input voltage by an offset voltage value. The magnitude of this offset voltage or the relationship between the input and output voltages of the level shifter circuit is adjustable or programmably selectable. Adjustment can be made after the integrated circuits is fabricated and packaged. One technique of making adjustments is to configure bits of data in the integrated circuit to indicate the offset voltage or other parameters. For example, these configuration bits can be implemented using latches, flip-flops, registers, memory cells, and other type of storage elements.
In another embodiment, present invention is an integrated circuit including a programmable level shifter circuit receiving a sample of an analog signal input to the integrated circuit. The level shifter circuit generates a level shifter voltage output above a voltage of the sample by an offset voltage, where the offset voltage is programmably selectable. The integrated circuit further includes an array of analog memory cells. The level shifter voltage output is connected to a memory cell to configure the memory cell to store the sample.
In a further embodiment, an integrated circuit of the present invention includes a programmable level shifter with an operational amplifier generating a level shifter output. An offset voltage between the level shifter output and an analog input depends on a value of capacitance connected between the analog input and an operational amplifier input. The value of the capacitance is programmably selectable. The integrated circuit includes an array of memory cells. The level shifter output is connected to configure a memory cell to store the analog input.
Moreover, the present invention includes a method of operating an integrated circuit. An analog signal input is provided. A sample of the analog signal input is taken. A first voltage above the sample input by a first offset value is generated. A second voltage above the sample by a second offset value is generated. A node of a memory cell is pulsed using the first voltage. A threshold voltage of the memory cell is evaluated using the second voltage, where the second voltage is connected to a control electrode of the memory cell. The memory cell is pulsed and evaluated until the threshold voltage of the memory cell is at a target value.
Another method of the present invention includes determining a stored threshold voltage of a memory cell by varying a voltage at a control electrode of the memory cell until the memory cell changes from conducting a first state to a second state. A playback output voltage, which is below the stored threshold voltage by an offset value, is generated by the using the stored threshold voltage.
Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the figures.
REFERENCES:
Haeberli Andreas M.
So Hock C.
Wang Cheng-Yuan Michael
Werner Carl W.
Wong Leon Sea Jiunn
Kim Jung Ho
Majestic, Parsons, Siebert & Hsue
SanDisk Corporation
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