Micron Technology Inc v. Sonrai Memory Ltd

1. Case Identification

• Case #: IPR2023-00909
• Patent #: 6,724,241
• Filed: May 8, 2023
• Petitioner(s): Micron Technology, Inc.
• Patent Owner(s): Sonrai Memory Ltd.
• Challenged Claims: 1-25

2. Patent Overview

• Title: Variable Charge Pump Circuit with Dynamic Load
• Brief Description: The ’241 patent discloses a charge pump circuit designed to generate voltages higher than an available power source, primarily for use in non-volatile memory devices. The technology aims to minimize output voltage ripple by employing a dynamic system comprising a plurality of selectable loads that are selectively coupled to the circuit’s output to match a preselected pump voltage.

3. Grounds for Unpatentability

Ground 1: Obviousness over Doluca and Buti - Claims 1-3, 24, and 25 are obvious over Doluca in view of Buti.

• Prior Art Relied Upon: Doluca (Patent 4,769,784) and Buti (Patent 5,872,733).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Doluca disclosed a charge pump circuit for memory devices that uses a general "charge bleeder" to regulate output voltage. However, Doluca lacked specific structural details for this bleeder. Buti allegedly remedied this deficiency by teaching a specific bleeder circuit with multiple bleeding paths, each controlled by a field-effect transistor (FET). Petitioner contended that these FETs function as the claimed "plurality of loads," and Buti's associated control circuitry, which activates the FETs based on output voltage, constitutes the claimed "load selector means."
  • Motivation to Combine: A person of ordinary skill in the art (POSITA), upon reviewing Doluca’s high-level disclosure of a charge bleeder, would have been motivated to consult references like Buti for known, concrete implementations of such circuits. The shared technical goal of regulating charge pump voltage for memory devices would have prompted this combination.
  • Expectation of Success: The proposed combination involved implementing a known circuit (Buti's bleeder) into a compatible system (Doluca's charge pump) to perform its intended and well-understood function, leading to a predictable and successful outcome.

Ground 2: Obviousness over Le and Ujiie - Claims 1 and 6-10 are obvious over Le in view of Ujiie.

• Prior Art Relied Upon: Le (Patent 6,424,570) and Ujiie (Japanese Application # S61-024094).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Le described a multi-stage charge pump that uses a generic "shunt regulator" to reduce voltage ripple but did not detail its structure. Ujiie was presented as disclosing the specific structure of such a shunt regulator, which uses switches (Q1, Q2) to selectively couple loads (diodes D1, D2) to the charge pump output. Petitioner argued that implementing Le's generic regulator with Ujiie's specific, functional circuit would result in the circuit claimed in the ’241 patent.
  • Motivation to Combine: A POSITA seeking to build the circuit in Le would have looked to other prior art, such as Ujiie, for an established design of a shunt regulator. The motivation stemmed from the need to find a concrete circuit structure to realize the functional block described in Le, with Ujiie providing a direct solution in the same technical field.
  • Expectation of Success: Combining the references was characterized as a straightforward integration of a known structural component (Ujiie) to realize a described function (in Le), a routine design choice with a high expectation of success.

Ground 3: Obviousness over Asano, Le, Ujiie, and Kuriyama - Claims 13-17, 19, and 21-23 are obvious over Asano in view of Le, Ujiie, and Kuriyama.

• Prior Art Relied Upon: Asano (Patent 4,506,350), Le (Patent 6,424,570), Ujiie (Japanese Application # S61-024094), and Kuriyama (Patent 6,373,325).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground targeted claims directed to a memory device. Petitioner argued that Asano provided the foundational memory system architecture (address bus, control circuit, memory array). The combination of Le and Ujiie, as argued previously, supplied the claimed charge pump with selectable loads. Kuriyama was introduced to teach additional control features, such as a circuit for shutting down the charge pump when its output exceeds a reference voltage and a regulator for adding loads to control ripple, allegedly meeting further limitations recited in the dependent claims.
  • Motivation to Combine: A POSITA would combine Asano's memory system with the improved Le/Ujiie charge pump as a design alternative. To further improve power efficiency and voltage regulation, the POSITA would be motivated to incorporate known control functionalities from a reference like Kuriyama, which explicitly addresses charge pump on/off control and multi-mode voltage regulation.
  • Expectation of Success: Petitioner argued that success would be expected, as the combination involved integrating well-understood sub-circuits, each performing its intended function within a predictable system architecture.
• Additional Grounds: Petitioner asserted additional obviousness challenges based on combinations including Hosono, Yang, and Kuriyama, but relied on similar design modification and implementation theories.

4. Key Claim Construction Positions

• "load" (claims 1, 13): Petitioner proposed two alternative constructions for this term. The broader construction defines "load" as any "device that receives electrical power." The narrower construction defines it as a "device that absorbs surplus charge to reduce voltage ripple." Petitioner maintained that the challenged claims are obvious under either interpretation.
• "load selector means" (claim 1): Petitioner contended this is a means-plus-function limitation. The recited function was identified as "choosing a load based on the target pump voltage," with the corresponding structure in the ’241 patent’s specification being a set of switches, their respective control signals, and potentially a controller that generates those signals.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial would be inappropriate under both 35 U.S.C. §325(d) and §314(a).
• Regarding §325(d) (Advanced Bionics), Petitioner asserted that the claims were allowed without any substantive rejection during prosecution and that the core prior art references relied upon in the petition (e.g., Doluca, Buti, Ujiie, Hosono) were not cited or considered by the examiner, constituting a material error.
• Regarding §314(a) (General Plastic/Fintiv), Petitioner argued that a prior IPR on the ’241 patent was filed by a different, unrelated petitioner and was terminated pre-FWD. Crucially, Petitioner filed a stipulation agreeing not to pursue in a parallel district court proceeding the same grounds raised in the petition, or any grounds that reasonably could have been raised, which under current USPTO guidance weighs dispositively against a Fintiv-based denial.

6. Relief Requested

• Petitioner requests institution of inter partes review and cancellation of claims 1-25 of Patent 6,724,241 as unpatentable.