Intel Corp v. R2 Semiconductor Inc

1. Case Identification

• Case #: IPR2017-00708
• Patent #: 8,233,250
• Filed: January 20, 2017
• Petitioner(s): Intel Corporation
• Patent Owner(s): R2 Semiconductor, Inc.
• Challenged Claims: 10-12, 23-26, 28, and 31

2. Patent Overview

• Title: Voltage Spike Protection Circuitry
• Brief Description: The ’250 patent discloses a voltage regulator with voltage spike protection circuitry, commonly known as a snubber circuit. The circuitry includes a dissipative element (resistor) and a charge-storage circuit (capacitor) to protect regulator components from voltage spikes. The alleged novelty centers on the method for calculating the resistance value of the dissipative element.

3. Grounds for Unpatentability

Ground 1: Claims 10-12 and 23-26 are obvious over Shekhawat in view of McMurray and Ozawa.

• Prior Art Relied Upon: Shekhawat (Patent 7,834,597), McMurray (1972 article, "Optimum Snubbers for Power Semiconductors"), and Ozawa (Japanese Application Publication No. H10-42573).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Shekhawat disclosed a standard voltage regulator with a snubber circuit (resistor and capacitor) for reducing voltage spikes. The key limitation added during prosecution—calculating the resistor’s value based on a lumped-element approximation of a transmission line’s characteristic impedance—was explicitly taught by McMurray. McMurray, described as a "classic snubber reference," provided the foundational equations for determining the optimal snubber resistance based on the circuit's total inductance (L) and capacitance (C). The term √L/C in McMurray’s equation is the definition of characteristic impedance, and using the total circuit inductance represents a lumped-element approximation. Ozawa taught the well-known technique of segmenting power converter circuits, including switches and their associated snubber circuits, into multiple parallel blocks.
  • Motivation to Combine: A POSITA would combine Shekhawat’s basic snubber circuit with McMurray’s well-known and widely used equations to optimize the circuit’s performance and effectively damp voltage spikes, which was Shekhawat's stated goal. Furthermore, a POSITA would be motivated to apply Ozawa’s segmentation technique to Shekhawat’s design to increase the circuit's overall power handling capacity and reduce ripple voltage, which are common and desirable goals in power converter design.
  • Expectation of Success: A POSITA would have a high expectation of success because the combination involved applying a classic, time-tested design formula (McMurray) and a conventional layout strategy (Ozawa) to a standard voltage regulator circuit (Shekhawat), leading to predictable improvements in performance.

Ground 2: Claims 28 and 31 are obvious over Shekhawat in view of Ozawa.

• Prior Art Relied Upon: Shekhawat (Patent 7,834,597) and Ozawa (Japanese Application Publication No. H10-42573).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground focused on the structural arrangement of the claimed circuit. Petitioner asserted that Shekhawat disclosed the fundamental voltage regulator with switching elements and a snubber circuit. Ozawa taught segmenting such circuitry into a plurality of parallel "switching block segments" and arranging the associated snubber components physically close to the switching segments they protect. Claims 28 and 31 require this specific arrangement, wherein each charge-storage circuit segment (capacitor) is physically closer to the switching block segment it protects than to any other.
  • Motivation to Combine: A POSITA would combine the teachings to improve the power handling capacity of the Shekhawat circuit, a known benefit of segmentation taught by Ozawa. Ozawa explicitly motivated placing snubber circuits in close proximity to their corresponding switches to minimize parasitic inductance in the wiring, which improves the effectiveness of the snubbering. This provided a direct and compelling reason to implement the physically close arrangement required by the challenged claims.
  • Expectation of Success: The combination represented a routine application of established circuit layout principles for mitigating parasitic effects. A POSITA would have reasonably expected that applying Ozawa's layout strategy to Shekhawat's circuit would successfully increase power capacity and improve snubber performance.

4. Key Claim Construction Positions

• "dissipative element": Petitioner argued this term is a means-plus-function limitation under 35 U.S.C. §112(f).
  • Function: "dissipates energy."
  • Structure: A "resistor." This construction was based on the ’250 patent's specification, which consistently depicted the "dissipative element" using the standard zig-zag resistor symbol and the letter "R" (e.g., Rsp).
• Alternative Construction: If the Board determined the term was not subject to means-plus-function analysis, Petitioner argued it should still be construed as a "resistor" under the broadest reasonable interpretation standard, as the specification provided no other structural embodiment. This construction was central to mapping the resistors disclosed in Shekhawat and McMurray to the claims.

5. Key Technical Contentions (Beyond Claim Construction)

• McMurray's Equation Teaches the "Lumped-Element" Limitation: A central technical contention was that McMurray's 1972 equations for snubber resistance directly satisfied the claim limitation requiring the value to be "based on a characteristic impedance of a lumped-element approximation of a transmission line." Petitioner contended that the mathematical term √L/C, which forms the basis of McMurray's calculation, is the fundamental definition of characteristic impedance. Further, using a single value "L" to represent the total "circuit inductance" inherently constitutes a "lumped-element approximation" of all distributed inductances (including parasitic inductances from wiring) in the circuit path, which functions as a transmission line.

6. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 10-12, 23-26, 28, and 31 of the ’250 patent as unpatentable under 35 U.S.C. §103.