Invalidity dossier
US 5172338
Multi-state EEprom read and write circuits and techniques
Current assignee: SanDisk Technologies LLC
Added 9/23/2026, 11:39:05 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US5172338A
Title: Multi-state EEprom read and write circuits and techniques
Patent number: US5172338A (also published as US5172338B1)
Application number: US07/508,273
Inventors: Sanjay Mehrotra, Eliyahou Harari, Winston Lee
Original assignee: SanDisk Corp (assignment recorded 1990-06-13 to SunDisk Corporation, a corp. of DE)
Current assignee listed: SanDisk Technologies LLC
Priority date: 1989-04-13
Filing date: 1990-04-11
Publication/grant date: 1992-12-15
Legal status: Expired – Lifetime (anticipated expiration 2014-07-08)
Purpose and plain-language scope
The patent concerns EEPROM memory circuits and methods for reading and writing cells that store more than two stable states — i.e., multi-state (multi-level) storage rather than simple binary storage. Per the classifications in the supplied text, the subject matter covers: storage elements having more than two stable states represented by steps (e.g., voltage, current, phase, frequency), using charge storage in a floating gate; programming/writing circuits and data input circuits; erasing circuits including block, array, word and group erase; sensing/reading circuits with differential sensing or reference/dummy cells; and verification of programming status, e.g., threshold voltage, overprogramming or underprogramming, and retention.
In plain terms, the excerpt indicates the patent addresses circuits and techniques for storing multiple data states per EEPROM cell and for reliably reading back and writing those states, including sensing against references and verifying programmed threshold levels.
Priority family filings noted in the excerpt: PCT/US1990/001984 (WO1990012400A1); EP90906720 (EP0539358B1); EP96114367 (EP0774759B1); EP96114368 (EP0778582B1); EP96115502 (EP0756287B1); JP2506478 (JPH04507320A); and corresponding DE publications.
What the excerpt does not establish
The supplied text contains no claims, no detailed description, and no drawings text. It therefore does not establish the specific claim scope, the exact circuit topologies, the number of states per cell, or any prior-art references relied upon. It also does not establish the accuracy of the listed assignees or legal-status assumptions, which the source itself disclaims. No litigation, ownership-transfer, validity, or prior-art analysis is made here.
Source: https://patents.google.com/patent/[US5172338](/patent/US5172338)/en
Generated 10/1/2026, 9:32:36 PM
Cases on file (0)
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Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
Proceedings on file (0)
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No PTAB proceedings on file. This patent has not been challenged via IPR, PGR, or CBM. The absence is itself a signal — well-asserted patents eventually attract IPRs. The LLM analysis below may surface filings the ODP feed hasn’t indexed yet.
PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
Earlier patents, publications, and products that may anticipate or render the claims unpatentable.
Obviousness
Combinations of prior art that suggest the claimed invention would have been obvious under 35 U.S.C. § 103.
Extensions
Patent term adjustments, term extensions, continuations, divisionals, family members, and expiration dates.
Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.