Western Digital Technologies Inc v. Longitude Licensing Ltd

1. Case Identification

• Case #: IPR2023-01230
• Patent #: 9,207,701
• Filed: July 20, 2023
• Petitioner(s): Western Digital Technologies, Inc.
• Patent Owner(s): Longitude Licensing Ltd.
• Challenged Claims: 1-18

2. Patent Overview

• Title: Supply Voltage Generating Circuit
• Brief Description: The ’701 patent discloses a supply voltage generating circuit for a semiconductor device, such as a memory chip. The circuit generates a boosted output voltage by selecting from one of two different input power supply voltages and dynamically changing the number of active booster stages in a charge pump based on which input voltage is selected.

3. Grounds for Unpatentability

Ground 1: Claims 1-18 are obvious over Zhang in view of Javanifard.

• Prior Art Relied Upon: Zhang (Patent 7,427,888) and Javanifard (Patent 5,767,735).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Zhang taught a charge pump circuit with a selector for choosing between two input voltages (a standard VCC and a higher VPP) to more quickly generate a desired output voltage. However, Zhang used a fixed-stage pump. Petitioner asserted that Javanifard remedied this deficiency by teaching a charge pump with a variable number of stages. Javanifard explicitly disclosed reconfiguring the number of active pump stages (e.g., from two stages to four stages) via switches to accommodate different input voltage levels or achieve a desired output level. The combination of Zhang’s input selection with Javanifard’s variable-stage configuration allegedly rendered all limitations of the independent claims obvious.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine the teachings to improve the performance and flexibility of Zhang’s multi-power-source system. Javanifard explicitly taught that using a variable-stage pump overcomes the disadvantages of fixed-stage pumps, such as poor efficiency and area usage, when needing to accommodate different power supply levels. This combination would yield the predictable benefits of improved efficiency, area reduction, and greater design flexibility.
  • Expectation of Success: A POSITA would have a reasonable expectation of success, as the combination involved applying Javanifard's known technique for improving charge pump flexibility to Zhang's known multi-source charge pump system to achieve predictable improvements.

Ground 2: Claims 1-18 are obvious over Javanifard alone.

• Prior Art Relied Upon: Javanifard (Patent 5,767,735).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Javanifard, through its different disclosed embodiments, taught all elements of the challenged claims. Embodiment 2 of Javanifard described a multi-power-source system that selects between different power sources (e.g., VCC and VPP) to supply a charge pump. Embodiments 1 and 3 of Javanifard described in detail a variable-stage charge pump where the number of stages can be reconfigured using switches.
  • Motivation to Combine: A POSITA would have been motivated to combine Javanifard's disclosed embodiments. The patent's stated object was to create a flexible charge pump that can "accommodate a given output level for different charge pump power supply input levels." Combining the multi-source input from Embodiment 2 with the variable-stage pump from Embodiments 1 and 3 was an obvious design choice to achieve the patent's own stated goals.
  • Expectation of Success: A POSITA would expect success, as it involved combining compatible features disclosed within a single prior art reference to achieve the reference's own objectives.

Ground 3: Claims 9 and 18 are obvious over combinations including Kang.

• Prior Art Relied Upon: Zhang (Patent 7,427,888), Javanifard (Patent 5,767,735), and Kang (a Dec. 2006 journal article on charge pump efficiency).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground built upon the combinations in Grounds 1 and 2 to address dependent claims 9 and 18, which further required the booster circuitry to comprise "capacitors formed using thin gate oxide transistors." Petitioner argued that the base combinations of Zhang and Javanifard (or Javanifard alone) established a variable-stage, multi-source charge pump. Kang was then introduced as teaching the use of thin-oxide MOSFETs for the pumping capacitors.
  • Motivation to Combine: Kang explicitly provided the motivation for its inclusion. It taught that using thin-oxide transistors as capacitors "can reduce the area of charge pumps greatly while keeping their driving capability." A POSITA, having designed the charge pump system taught by Zhang and Javanifard, would have been motivated to incorporate Kang's teaching to achieve the well-known and desirable benefit of reducing the circuit's physical size on the semiconductor die.
  • Expectation of Success: The modification was a predictable optimization, applying a known technique for area reduction to a standard component (pumping capacitors) of a charge pump circuit.

4. Arguments Regarding Discretionary Denial

• Arguments against Fintiv Denial: Petitioner argued that discretionary denial under §314(a) based on Fintiv factors would be inappropriate. A parallel district court case exists, but it is in its earliest stages with no trial date set or significant investment made. Furthermore, Petitioner stated it would stipulate not to pursue the same invalidity grounds in the district court if the IPR is instituted, mitigating concerns of duplicative efforts. Petitioner also asserted that the petition presents compelling evidence of unpatentability, weighing in favor of institution per the Director's guidance.
• Arguments against §325(d) Denial: Petitioner contended that denial under §325(d) was unwarranted because the primary references—Zhang, Javanifard, and Kang—were not considered by the Examiner during the original prosecution. Petitioner argued these references were not cumulative of the previously considered art because they directly taught the key limitation the Examiner relied upon for allowance: changing the number of booster stages in response to the selection of an input power supply.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-18 of the ’701 patent as unpatentable.