Infineon Tech AG v. Volterra Semiconductor Corporation

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Infineon Technologies AG (Germany)
  • Defendant: Volterra Semiconductor Corporation (Delaware)
  • Plaintiff’s Counsel: McDermott Will & Emery LLP
• Case Identification: Infineon Technologies AG v. Volterra Semiconductor Corporation, 1:10-cv-00047, D. Del., 01/21/2010
• Venue Allegations: Venue is alleged to be proper in the District of Delaware because the Defendant, Volterra Semiconductor Corporation, is a Delaware corporation and therefore resides in the judicial district.
• Core Dispute: Plaintiff alleges that Defendant’s voltage regulators and pulse width modulation controllers infringe four patents related to the structure of semiconductor power devices and circuit designs for amplifying electrical signals.
• Technical Context: The lawsuit concerns foundational technologies in analog and mixed-signal power management semiconductors, which are critical components in a wide range of electronic applications, including computing, networking, and consumer markets.
• Key Procedural History: The complaint does not allege any prior litigation, inter partes review proceedings, or licensing history related to the patents-in-suit.

Case Timeline

Date	Event
1991-07-24	U.S. Patent No. 5,402,017 Priority Date
1995-03-28	U.S. Patent No. 5,402,017 Issued
1997-02-12	U.S. Patent No. 5,945,730 Priority Date
1999-08-31	U.S. Patent No. 5,945,730 Issued
2001-08-07	U.S. Patent No. 6,621,343 Priority Date
2003-09-16	U.S. Patent No. 6,621,343 Issued
2003-09-26	U.S. Patent No. 7,095,281 Priority Date
2006-08-22	U.S. Patent No. 7,095,281 Issued
2010-01-21	Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 5,945,730, "SEMICONDUCTOR POWER DEVICE", Issued Aug. 31, 1999

The Invention Explained

• Problem Addressed: The patent describes a challenge in high-current lateral power transistors (LDMOS), where the electrical resistance of the metal interconnects (on-resistance, or Rdson) leads to significant power dissipation and heat. (’730 Patent, col. 1:16-24). Prior solutions, such as using multiple wire bonds or depositing thick copper layers, were described as expensive, complex, and potentially increasing the overall size of the device. (’730 Patent, col. 1:31-60).
• The Patented Solution: The invention proposes a structure to reduce this resistance by providing a more direct electrical connection to the active areas of the semiconductor. It consists of a specialized "frame" made of a high-conductivity material that sits over the transistor die. This frame has "connecting portions" that make contact with "bumps" placed directly on the device's metal conductors. This arrangement creates a low-resistance path for current, mitigating the need for long, resistive paths to bonding pads at the chip's periphery. (’730 Patent, Abstract; col. 2:1-7, Fig. 1-2).
• Technical Importance: This design aimed to enable the creation of smaller, more power-efficient transistors capable of handling higher currents by directly addressing the issue of interconnect resistance without adding costly or complex manufacturing steps. (’730 Patent, col. 4:49-59).

Key Claims at a Glance

• The complaint asserts infringement of the patent generally, without specifying claims. Independent claim 1 is representative and includes the following essential elements:
  • First and second semiconductor regions.
  • A plurality of first metal conductors coupled to the first semiconductor region, each having at least one bump.
  • A plurality of second metal conductors coupled to the second semiconductor region, each having at least one bump.
  • A frame of high conductivity material with first and second connection portions for connecting to the bumps on the first and second metal conductors, respectively, to provide external connections.

U.S. Patent No. 7,095,281, "DIFFERENTIAL AMPLIFIER ARRANGEMENT WITH CURRENT REGULATING CIRCUIT AND METHOD FOR OPERATING A DIFFERENTIAL AMPLIFIER ARRANGEMENT", Issued Aug. 22, 2006

The Invention Explained

• Problem Addressed: The patent identifies a fundamental trade-off in low-noise amplifier design. To achieve a good signal-to-noise ratio, a high DC bias current is desirable. However, in conventional designs, this high current flowing through load resistors causes a large voltage drop, which limits the output voltage swing and reduces the operating range of the input transistors. (’281 Patent, col. 1:55-65).
• The Patented Solution: The invention discloses a differential amplifier circuit that uses a common-mode feedback loop to manage the bias current. A regulable current source is positioned between the input transistors and their associated load resistors. A comparison circuit measures the common-mode voltage at the output, compares it to a fixed reference voltage, and generates a control signal. This signal instructs the regulable current source to divert, or "switch out," a portion of the DC bias current so that it does not flow through the load resistors. This maintains a low voltage drop across the loads, preserving output swing, while still allowing a high bias current to flow through the input transistors for low-noise performance. (’281 Patent, Abstract; col. 5:44-67).
• Technical Importance: This architecture provides a method to decouple the requirements for low noise (high bias current) and high output swing (low voltage drop at the load), enabling more efficient amplifier designs using standard, space-saving nonreactive resistors. (’281 Patent, col. 3:1-10).

Key Claims at a Glance

• The complaint asserts infringement of the patent generally, without specifying claims. Independent claim 1 is representative and includes the following essential elements:
  • A DC current source and first and second controllable paths (e.g., input transistors).
  • First and second loads coupled to the controllable paths via respective cascode circuits.
  • First and second taps between the loads and cascode circuits, forming an output.
  • A comparison mechanism that compares signals from the taps to a reference signal.
  • A regulable current source, controlled by the comparison mechanism, connected to the first controllable path.

U.S. Patent No. 5,402,017, "CONTROLLABLE CIRCUIT CONFIGURATION FOR COMPENSATING FLUCTUATIONS IN AN AMPLIFIER", Issued Mar. 28, 1995

Technology Synopsis

The patent addresses performance variations in amplifiers caused by manufacturing tolerances and temperature changes. (’017 Patent, col. 1:12-21). The proposed solution is a circuit architecture where an amplifier and a reference current source are built using the same technology to ensure they experience similar fluctuations. A multiplier circuit, controlled by an external signal, adjusts the current from the reference source before it is used to control the amplifier, thereby compensating for the shared fluctuations. (’017 Patent, Abstract).

Asserted Claims

The complaint does not specify which claims are asserted.

Accused Features

The complaint alleges that Defendant's "pulse width modulation controllers" infringe the ’017 patent. (Compl. ¶20).

U.S. Patent No. 6,621,343, "OPEN LOOP VARIABLE GAIN AMPLIFIER USING REPLICA GAIN CELL", Issued Sep. 16, 2003

Technology Synopsis

The patent seeks to overcome speed and bandwidth limitations of conventional variable gain amplifiers (VGAs), particularly those with closed-loop feedback designs. (’343 Patent, col. 1:8-16). The invention is an open-loop VGA that uses a "replica gain cell" operating in parallel to the main signal path. This replica cell contains a servo loop that generates precise gain and common-mode control signals based on a stable reference. These control signals are then applied to the gain cells in the main signal path, enabling high-speed, stable amplification that is robust against process and temperature variations without the inherent speed penalties of a feedback loop in the signal path itself. (’343 Patent, Abstract).

Asserted Claims

The complaint does not specify which claims are asserted.

Accused Features

The complaint alleges that Defendant's "voltage regulators" infringe the ’343 patent. (Compl. ¶25).

III. The Accused Instrumentality

Product Identification

The complaint identifies the accused instrumentalities as product categories rather than specific models. These are "pulse width modulation controllers" and "voltage regulators" designed, developed, and sold by Defendant Volterra. (Compl. ¶¶ 3, 9, 15, 20, 25).

Functionality and Market Context

The complaint alleges these products are analog and mixed-signal power management semiconductors for the computing, storage, networking, and consumer markets. (Compl. ¶3). The complaint does not provide further technical detail regarding the specific circuit architecture, packaging, or operational characteristics of the accused products.

IV. Analysis of Infringement Allegations

The complaint makes general allegations of infringement without providing a detailed technical mapping of accused product features to claim elements. Consequently, a claim-chart summary table cannot be constructed based on the pleading. The infringement theories are stated in conclusory terms.

• ’730 Patent Infringement Allegations: The complaint alleges that Defendant’s "voltage regulators" infringe the ’730 patent. (Compl. ¶9). An infringement analysis would likely focus on whether the physical construction of the accused regulators embodies the structural elements of a claim like independent claim 1. This raises the question of whether the packaging and interconnect technology used in the accused products constitutes a "frame" with "connecting portions" that contact "bumps" on the "metal conductors" in the manner claimed.
• ’281 Patent Infringement Allegations: The complaint alleges that Defendant's "pulse width modulation controllers" infringe the ’281 patent. (Compl. ¶15). An infringement analysis would center on the circuit architecture within the accused controllers. A key question is whether these circuits employ a feedback mechanism where a "comparison mechanism" regulates a "regulable current source" to divert a portion of the DC bias current away from the circuit's load, as required by claims such as independent claim 1.

No probative visual evidence provided in complaint.

V. Key Claim Terms for Construction

The complaint’s lack of detail precludes a definitive identification of disputed terms. However, based on the technology and accused product categories, the following terms may be central to the dispute.

• Term from the ’730 Patent: "frame"

  • Context and Importance: This term is the central structural element of the invention. Its construction will determine whether the patent reads on a broad category of lead frame and packaging solutions or is limited to a more specific structure. Practitioners may focus on this term because the allegedly infringing "voltage regulators" (Compl. ¶9) necessarily include some form of packaging and electrical connection, and the dispute will likely concern whether that structure meets the definition of the claimed "frame".
  • Intrinsic Evidence for a Broader Interpretation: The claim language is general, defining the term by its function and material: "a frame formed of high conductivity material, the frame comprising a plurality of first connection portions..." (’730 Patent, col. 5:24-29).
  • Intrinsic Evidence for a Narrower Interpretation: The preferred embodiment describes a specific implementation where the frame is a "copper pattern...formed on a polymer tape substrate" (’730 Patent, col. 3:23-27), with connecting portions that extend over the metal conductors in a particular orientation. This may support a narrower construction tied to this embodiment.

• Term from the ’281 Patent: "regulable current source"

  • Context and Importance: This element is the active component in the patent's novel feedback loop. The infringement analysis for the accused "pulse width modulation controllers" (Compl. ¶15) will depend on whether their internal current-control circuitry functions as the claimed "regulable current source".
  • Intrinsic Evidence for a Broader Interpretation: Claim 1 defines the element by its function: a source that is "regulated by the control signal from the comparison mechanism." (’281 Patent, col. 12:50-54). This is a functional definition that could potentially cover various circuit implementations.
  • Intrinsic Evidence for a Narrower Interpretation: The specification explains that the purpose of this source is to "discharge a part of the DC bias current" so it does not flow through the load, thereby reducing voltage drop. (’281 Patent, col. 5:48-52). This suggests a specific function of diverting or "switching out" current, which may be argued as a required functional limitation for any infringing structure.

VI. Other Allegations

• Indirect Infringement: The complaint makes boilerplate allegations of indirect and contributory infringement for all four patents without pleading specific underlying facts, such as the provision of instruction manuals or design specifications that would encourage or enable an infringing use by a third party. (Compl. ¶¶ 9, 15, 20, 25).
• Willful Infringement: The complaint specifically alleges that infringement of the ’730 patent "has been and continues to be willful and deliberate and with full knowledge of said patent." (Compl. ¶12). The prayer for relief also singles out the ’730 patent for a finding of willfulness, but not the other three patents-in-suit. (Compl. p. 6, ¶B).

VII. Analyst’s Conclusion: Key Questions for the Case

• A primary issue will be one of evidentiary specificity. The complaint uses a "notice pleading" style, identifying only broad product categories. A key hurdle for the Plaintiff will be to move from these general allegations to concrete proof, demonstrating through discovery that specific, identified Volterra products contain circuitry and structures that practice the limitations of the asserted patent claims.
• The case will also present a question of claim scope versus technological evolution. The asserted patents have priority dates spanning from 1991 to 2003. A central question for the court will be how to construe claim terms conceived in the context of one technological era—such as the '730 patent's structural "frame" or the '281 patent's specific "regulable current source" topology—with respect to the potentially different packaging and circuit designs used in Defendant’s products.