Intel Corp v. R2 Semiconductor Inc

1. Case Identification

• Case #: IPR2017-00707
• Patent #: 8,233,250
• Filed: January 20, 2017
• Petitioner(s): Intel Corporation
• Patent Owner(s): R2 Semiconductor, Inc.
• Challenged Claims: 1-4, 7-9, 13-17, 20-22, and 29

2. Patent Overview

• Title: Voltage Spike Protection Circuitry and Method of Use
• Brief Description: The ’250 patent discloses a voltage spike protection circuit, commonly known as a snubber circuit, for use in switching voltage regulators. The technology’s purported novelty is a specific method for selecting the resistance value of a “dissipative element” (resistor) based on a lumped-element approximation of the circuit's parasitic inductance and capacitance to mitigate voltage spikes.

3. Grounds for Unpatentability

Ground 1: Obviousness over Shekhawat and McMurray - Claims 1-4, 7-9, 13-17, 20-22, and 29 are obvious over Shekhawat in view of McMurray.

• Prior Art Relied Upon: Shekhawat (Patent 7,834,597) and McMurray (a 1972 IEEE publication titled "Optimum Snubbers for Power Semiconductors").
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Shekhawat disclosed all the physical components recited in independent claim 1: a voltage regulator containing a snubber circuit with a resistor (“dissipative element”) and a capacitor (“charge-storage circuit”) to protect against voltage spikes. Petitioner asserted that the key limitation added during prosecution to achieve allowance—calculating the resistor’s value based on the characteristic impedance of a lumped-element approximation of a transmission line—was explicitly taught decades earlier by McMurray. McMurray, a foundational reference on snubber design not considered by the Examiner, provided the exact equations to calculate an optimal snubber resistance based on the circuit’s total inductance (L) and capacitance (C), which is equivalent to being based on the characteristic impedance (sqrt(L/C)).
  • Motivation to Combine: Petitioner asserted that a person of ordinary skill in the art (POSITA) implementing the snubber circuit described in Shekhawat would be motivated to optimize its performance to effectively reduce voltage spikes and prevent component damage. To achieve this, a POSITA would naturally consult a classic, well-known reference like McMurray to find the standard design equations for calculating the snubber resistor value, which was a routine engineering task.
  • Expectation of Success: Petitioner contended that because the combination involved applying McMurray’s established mathematical formulas to the standard circuit topology disclosed in Shekhawat, a POSITA would have had a high expectation of success. The application of these principles was entirely predictable and would have yielded the desired result of damping voltage spikes.
  • Key Aspects: The central thrust of Petitioner’s argument was that the very feature the Patent Owner relied on to argue novelty and secure the patent—the specific formula for calculating the resistor's value—was, in fact, well-known and routine in the art for over 30 years before the patent's priority date, as demonstrated by the McMurray reference. The combination of Shekhawat's circuit and McMurray's classic design methodology rendered the claims obvious.

4. Key Claim Construction Positions

• "dissipative element": Petitioner dedicated significant argument to this term, contending it should be construed under 35 U.S.C. §112(f) as a means-plus-function term.
  • Proposed Construction: The claimed function is "to dissipate energy," and the only corresponding structure disclosed in the ’250 patent specification is a resistor, identified by the symbol "Rsp" and standard zig-zag line diagrams.
  • Alternative Construction: Petitioner argued that if the Board did not find the term to be governed by means-plus-function rules, it should still be construed as a "resistor" under the broadest reasonable interpretation standard. This was based on the specification consistently and exclusively using resistor symbols and terminology to describe the element. This construction was central to mapping the resistor in Shekhawat's snubber circuit to the claims.

5. Key Technical Contentions (Beyond Claim Construction)

• Lumped-Element Approximation: Petitioner asserted that McMurray’s method of creating an "equivalent circuit" for analysis inherently teaches a "lumped-element approximation" as claimed. McMurray’s formulas required consolidating all relevant circuit inductances into a single variable "L" and all relevant capacitances into a single variable "C" to calculate the characteristic impedance. Petitioner argued this is the essence of creating a lumped-element model for a transmission line, directly teaching a key claim limitation.
• Matching Characteristic Impedance (Claim 29): Petitioner argued that McMurray teaches that an "underdamped" condition is of most practical importance and shows that a damping factor of 0.5 is an exemplary, optimal design choice. Applying this damping factor of 0.5 to McMurray's own resistance formula (R = 2ζ * sqrt(L/C)) results in the resistance R being equal to the characteristic impedance (sqrt(L/C)), thereby explicitly teaching the limitation of claim 29.

6. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 1-4, 7-9, 13-17, 20-22, and 29 of Patent 8,233,250 as unpatentable under 35 U.S.C. §103.