Static information storage and retrieval – Analog storage systems
Reexamination Certificate
1999-06-29
2001-02-06
Fears, Terrell W. (Department: 2824)
Static information storage and retrieval
Analog storage systems
C365S207000
Reexamination Certificate
active
06185119
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 an integrated circuit memory capable of storing analog information. This integrated circuit may be referred to as an analog memory. The integrated circuit has nonvolatile memory cells capable of multilevel or analog voltage level storage. In addition to being able to store analog signals in analog form, the integrated circuit can also be used to store digital information in digital form. An analog input signal or other data is input to the integrated circuit and is sampled a sampling rate that is user selectable. Each sample of the input signal is stored in a memory cell. The analog signal is stored without the need for analog-to-digital (A/D) conversion. The analog input signal may be from a transducer which converts images, sound, actions, or other real world information into analog electrical impulse.
The integrated circuit memory has an internal signal path that is differential. This enhances the precision with which the signal is stored in the memory cells. Among other advantages a fully differential signal pass has inherently an improved common-mode noise rejection. Furthermore, the dynamic range is doubled which may lead to a higher signal to noise ratio and is suitable for low voltage applications. To store analog information the analog input to the integrated circuit has a positive (+) and negative (−) input. The analog input is connected to a preamplifier to amplify the input signal. The preamplifier is fully differential and has a positive and negative output. The preamplifier output is connected to a low pass filter. The filter has positive and negative outputs. These positive and negative outputs are connected to level shifter circuitry. The level shifter performs a sample and hold operation, an amplification, a voltage shift, and a differential to single ended conversion.
The stored analog information is retrieved by means of a slow ramp circuit. The playback level shifter takes the single-ended output of the slow ramp circuit and performs a voltage shift, an attenuation, and a single ended to fully differential conversion. The differential playback level shifter output is connected to a low pass filter, which is fully differential. The low pass filter has positive and negative outputs. These are connected to an output buffer or amplifier to amplify the signal. The output amplifier is also fully differential and provides positive and negative outputs.
The integrated circuit has a master-slave biasing scheme. A master bias generator generates a master bias voltage that is connected to a number of slave bias generators. This master bias voltage may be based on a bandgap voltage reference. The slave bias generators use the master bias voltage to generate a number of slave bias voltages. These slave bias voltages are connected to the various components of the integrated circuit. This scheme of connecting different slave bias generators to different components improve the isolation of the bias voltages among the components. It is less likely that components which couple noise into its slave bias generator will affect the other components connected to different slave bias generators. Also, if a component of the integrated circuit is not being used, its slave bias generator can be disabled to save power.
The integrated circuit has a squelch circuit to attenuate its output signal when an input to the squelch circuit is below threshold level. The squelch circuit essentially greatly attenuates background noise. In effect, there will be a greater signal to noise ratio at the output of the integrated circuit.
In an embodiment, the invention is an integrated circuit including an analog data differential input and a preamplifier circuit. The preamplifier circuit is connected to amplify an analog signal at the analog data differential input with a first gain, where an amplified output signal is provided at a first differential output of the preamplifier circuit. A low pass filter circuit is connected to the preamplifier differential output. The low pass filter circuit provides samples of the analog signal at a second differential output. A first level shifter circuit is connected to the second differential output, where the first level shifter circuit provides a first level shifter output signal at a first offset voltage above a level of a sample at the second differential output. The first level shifter output is connected to an arra
Haeberli Andreas M.
So Hock C.
Wang Cheng-Yuan Michael
Werner Carl W.
Wong Leon Sea Jiunn
Fears Terrell W.
Majestic, Parsons, Siebert & Hsue
SanDisk Corporation
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