NEC Corp. v. HYUNDAI ELECTRONICS INDUSTRIES CO.

30 F. Supp. 2d 546, 1998 U.S. Dist. LEXIS 19037, 1998 WL 838451
CourtDistrict Court, E.D. Virginia
DecidedDecember 2, 1998
DocketC.A. 97-1967, 97-1968, 97-1969, 97-2031 and 98-118
StatusPublished

This text of 30 F. Supp. 2d 546 (NEC Corp. v. HYUNDAI ELECTRONICS INDUSTRIES CO.) is published on Counsel Stack Legal Research, covering District Court, E.D. Virginia primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
NEC Corp. v. HYUNDAI ELECTRONICS INDUSTRIES CO., 30 F. Supp. 2d 546, 1998 U.S. Dist. LEXIS 19037, 1998 WL 838451 (E.D. Va. 1998).

Opinion

MEMORANDUM OPINION

ELLIS, District Judge.

Twenty patents covering different semiconductor circuitry devices and fabrication *548 processes are at issue in these consolidated patent infringement actions, twelve of which are asserted by NEC Corporation and eight of which are asserted by Hyundai Electronics Industries Co. 1 One of these patents, NEC’s U.S. Patent No. 4,054,865 (the ’865 patent), entitled “Sense Latch Circuit For a Bisectional Memory Array,” is now before the Court on the parties’ cross motions for summary judgment on the issue of infringement and on Hyundai’s motion for summary judgment on the issue of validity. Disposition of these motions requires claim construction under Markman v. Westview Instruments, Inc., 517 U.S. 370, 116 S.Ct. 1384, 134 L.Ed.2d 577 (1996), which, in turn, leads to the conclusion that Hyundai’s products do not literally infringe the ’865 patent, but that remaining disputed factual issues preclude summary judgment on the issues of validity and infringement under the doctrine of equivalents.

I. The ’865 Patent

The ’865 patent involves the circuitry connecting the sense amplifiers within a memory cell array and the input/output line, which carries information in and out of the memory cells. In particular, the ’865 patent relates to the manner in which an individual memory cell in a two-dimensional memory cell array is accessed, either in a “read” operation, where the value of the data stored in the memory cell is determined, or in a “write” operation, where the value of the individual data bit is stored in the cell. Claim 1 of the ’865 patent concerns the DRAM “read” function and claims 6 through 8 concern the DRAM “write” function.

A dynamic random access memory device (DRAM) is a basic type of memory chip that stores logic information in the form of binary digits, or “bits.” A bit may have a value of either “1” (signifying a high charge) or “0” (signifying a low charge). Each individual memory cell within a DRAM stores an electrical charge that determines the value of one data bit of information. The cells are connected to the circuitry outside the memory array through a grid of electrical lines known as “bit lines” and “word lines” with each word line identified by a unique “row address” and each bit line identified by a unique “column address.” An individual memory cell can be accessed by presenting the DRAM with the unique column address and row address combination corresponding to the cell’s location. Information in the form of electrical charge passes into and out of a selected memory cell through its corresponding bit line.

To read a particular memory cell, a signal is applied to the particular word line that is connected to that memory cell. In this fashion, power is applied to every memory cell in the row containing the selected cell because all cells in the row are attached to the same word line. To isolate the selected memory cell from all the other cells in the row along the activated word line, only the particular bit line and sense amplifier associated with the selected memory cell are “sensed” to determine the state of the cell. Column decoders control gates that select the particular bit line connected to a selected memory cell. Thus, a particular' memory cell is accessed by providing an activation signal through the word line connected to a row of memory cells containing the selected cell, and sensing the bit lines connected to the column that includes the selected memory cell. In a write operation, the same basic operation occurs, but in this event, a write gate is activated, allowing information to flow through the input/output line and into the memory cells.

The prior art as identified in the ’865 patent uses an “unbalanced” sensing scheme. The individual sense amplifiers are connected to the input/output line for the memory array through a column decoder and a gate located on only one side of the sense amplifier, through bit lines lying on only one side of the amplifier. For memory cells lying both above and below the sense amplifier, the output passes through this gate and column decoder to the output amplifier. There, the output *549 amplifier compares the signal coming from one side of the sense amplifier with a reference voltage to determine the value of that signal. Similarly, in “write” operations, a single write gate lying on one side of the sense amplifiers is used to apply a signal to reach cells on both sides of the sense amplifier. Thus, in the prior art, represented in Figure 1 of the ’865 patent, 2 the array of memory cells is divided into two halves by a series of sense amplifiers, but the individual memory cells in both halves are accessed from only one side during both read and write operations. In this prior art, output amplifiers, which amplify the signals created by the relatively small sense amplifiers, function by comparing the output signal on one side of the sense amplifier with a reference voltage and then sending a logical “1” or “0” to the output terminal depending on the relative voltage level of the signal.

In contrast to this “unbalanced” sensing scheme, the ’865 patent relies on the concept of “balanced” sensing. As illustrated by Figure 4 of the ’865 patent, 3 column decoders and gates are located on both sides of the sense amplifiers, one at the top of the memory cell array and one at the bottom of this array. Thus, each of the two bit lines in a bit line pair has its own input/output line, and each input/output line is operatively connected with the output amplifier during a read operation. In a read operation, signals from both bit lines of a bit line pair are transferred to an output amplifier when a word line is activated. The signals from both bit lines (which will be complementary to one another, based on the operation of the sense amplifier) will be transferred through their respective gates on each side of the memory cell array activated by their respective column decoders to the output sense amplifier. The arrangement shown as the invention in the ’865 patent is called ‘balanced’ because both sides of the sense amplifier output are used equally. Thus, instead of comparing the output of one side to a reference voltage, the output amplifier compares the two complementary signals from both sides of the sense amplifier, resulting in a-faster, more reliable read operation.

Similarly, in a “write” operation, a pair of write gates are used, which apply complementary signals through a pair of gates activated by a patr of column decoders to write a bit of data in the selected memory cell. Once again, the operation is “balanced” in that signals are applied from both sides of the sense amplifier.

A specific problem with early dynamic sense amplifiers was their inability to perform a “read modify write” (RMW) operation. In an RMW cycle, the memory cell is first read; then new information from outside the chip is written into the memory location that has just been read. While this cycle is quite efficient in terms of system operation, it requires that the new information overwrite the potentially opposite state of the sense amplifier.

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30 F. Supp. 2d 546, 1998 U.S. Dist. LEXIS 19037, 1998 WL 838451, Counsel Stack Legal Research, https://law.counselstack.com/opinion/nec-corp-v-hyundai-electronics-industries-co-vaed-1998.