DCT
6:25-cv-00449
Reed Semiconductor Corp v. Monolithic Power Systems Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Reed Semiconductor Corp. (Delaware)
- Defendant: Monolithic Power Systems, Inc. (Delaware)
- Plaintiff’s Counsel: Morgan, Lewis & Bockius LLP
- Case Identification: 6:25-cv-00449, W.D. Tex., 09/30/2025
- Venue Allegations: Plaintiff alleges venue is proper in the Western District of Texas because Defendant maintains a regular and established place of business in the district through resident employees and the use of third-party distributors that store accused products.
- Core Dispute: Plaintiff alleges that Defendant’s power management integrated circuits infringe a patent related to a power supply architecture designed to isolate control circuitry from electrical noise.
- Technical Context: The technology at issue involves methods for designing switching power supplies to ensure stable and reliable operation, a critical requirement for a wide range of modern electronic devices.
- Key Procedural History: The complaint notes that Defendant has previously initiated its own patent litigation in the Western District of Texas, which Plaintiff presents to argue against any potential claims of inconvenience or unfairness of the forum.
Case Timeline
| Date | Event |
|---|---|
| 2005-12-09 | U.S. Patent No. 7,960,955 Priority Date |
| 2011-06-14 | U.S. Patent No. 7,960,955 Issue Date |
| 2019 | Plaintiff Reed Semiconductor Corp. founded |
| 2025-09-30 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,960,955 - "Power Supply Device, Electronic Device Using the Same, and Semiconductor Device"
- Patent Identification: U.S. Patent No. 7,960,955, "Power Supply Device, Electronic Device Using the Same, and Semiconductor Device," issued June 14, 2011 (the "’955 Patent").
The Invention Explained
- Problem Addressed: The patent’s background section describes how switching power supplies, which are common in electronic devices, generate high-frequency electrical "switching noise." This noise can be transmitted through power supply wiring to other sensitive components, particularly the reference voltage source that is used to regulate the system's output. When the reference voltage is destabilized by noise, the entire power supply's stepping-up or stepping-down operation can be hindered. (’955 Patent, col. 1:41-49).
- The Patented Solution: The invention proposes an architecture that isolates the sensitive control circuitry from this noise. It introduces a linear regulator that takes the "noisy" input voltage and produces a separate, stable, "clean" output voltage. This clean voltage is then used exclusively to power the controller for the switching power supply and the reference voltage source. By creating this isolated power domain for the control logic, the invention prevents the switching noise from the main power path from corrupting the reference voltage, thereby ensuring stable operation. (’955 Patent, Abstract; col. 2:59-63).
- Technical Importance: This design provides a method for enhancing the stability and reliability of power converters, a crucial factor for performance in densely packed and noise-sensitive electronic systems. (’955 Patent, col. 2:50-54).
Key Claims at a Glance
- The complaint asserts at least independent claim 1. (Compl. ¶48).
- The essential elements of independent claim 1 are:
- A switching power supply which stabilizes an input voltage.
- A reference voltage source which generates a predetermined reference voltage.
- A linear regulator which stabilizes the input voltage, based on the reference voltage from the source.
- Wherein an output voltage of the linear regulator is supplied as a power supply voltage to both a controller of the switching power supply and the reference voltage source.
- Wherein the input voltage is not directly supplied to the controller as a power supply voltage.
- The complaint makes general allegations of infringement of "one or more claims," a common reservation of the right to assert additional claims, including dependent claims, during litigation. (Compl. ¶17).
III. The Accused Instrumentality
Product Identification
- The complaint identifies a broad family of "MPS Accused Products," described as "power management products that include a linear regulator to stabilize an input voltage." (Compl. ¶12, ¶40). The NB680 integrated circuit is identified as a representative example of the accused products. (Compl. ¶49).
Functionality and Market Context
- The accused products are described as "high frequency, synchronous rectified, switch-mode converter[s]" designed to provide a regulated voltage from a wide input supply range with "excellent load and line regulation." (Compl. ¶50). The complaint alleges these components are sold through distributors and directly from Defendant's website for incorporation into a variety of downstream electronic devices. (Compl. ¶12, ¶41).
IV. Analysis of Infringement Allegations
Claim Chart Summary
- The complaint provides a narrative infringement theory against the representative NB680 product, supported by excerpts from its datasheet. The complaint's allegations regarding claim 1 are summarized below.
’955 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a switching power supply which stabilizes the input voltage | The NB680 is described as a "switch-mode converter" that provides "excellent load and line regulation," thereby stabilizing the input voltage. | ¶50 | col. 4:43-47 |
| a reference voltage source which generates a predetermined reference voltage | The NB680 datasheet is alleged to show an internal "reference voltage (VREF)" used to regulate the output voltage, satisfying this element. | ¶51 | col. 4:60-61 |
| a linear regulator which stabilizes the input voltage, based on the reference voltage generated by the reference voltage source | The complaint alleges the NB680 contains a "built-in 100 mA standby linear regulator" (LDO). | ¶52 | col. 4:60-61 |
| wherein an output voltage of the linear regulator is supplied as a power supply voltage of a controller of the switching power supply and the reference voltage source | The complaint points to a functional block diagram from the NB680 datasheet, which allegedly shows the output of the internal linear regulator (VCC) powering the "‘POR & Reference’ Block" and other control logic. The complaint includes a functional block diagram for the NB680. (Compl. ¶53). | ¶53 | col. 2:59-63 |
| and the input voltage is not directly supplied to the controller as a power supply voltage | The same functional block diagram is alleged to show that the main input voltage (VIN) is not connected to power the controller circuit, which is instead powered by the linear regulator's output. | ¶53 | col. 12:61-64 |
Identified Points of Contention
- Scope Questions: A potential issue may arise from the claim language requiring the linear regulator's output to supply power to "a controller... and the reference voltage source." The complaint alleges the NB680's "‘POR & Reference’ Block" is both the reference source and part of the controller. The litigation may involve a dispute over whether this integrated architecture meets the claim's requirement for powering what could be interpreted as two distinct functional blocks.
- Technical Questions: The infringement case for the negative limitation—that the input voltage is "not directly supplied to the controller"—appears to rely heavily on the functional block diagram provided in the product datasheet. (Compl. ¶53). A key technical question will be what evidence, beyond this high-level diagram, demonstrates the absence of such a connection within the physical circuitry of the accused chip.
V. Key Claim Terms for Construction
The Term: "controller of the switching power supply"
- Context and Importance: The definition of this term is central to the infringement analysis, as it identifies the specific circuitry that must be powered by the linear regulator and isolated from the main input voltage. The parties may dispute what specific components within the accused integrated circuit constitute the "controller."
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification describes the "switching controller 40" in functional terms as the component that "controls base voltage of the switching transistor Tr1, and controls ON and OFF states thereof." (’955 Patent, col. 5:1-3). This functional description may support an interpretation that covers any collection of logic blocks performing that role.
- Evidence for a Narrower Interpretation: The patent’s FIG. 1 depicts the "SWITCHING CONTROLLER 40" as a distinct, singular block. This depiction could be used to argue that the term should be construed more narrowly to mean a discrete, identifiable module, not a diffuse set of circuits spread across the chip.
The Term: "not directly supplied"
- Context and Importance: As a negative limitation, the infringement analysis requires proving the absence of a particular connection. The meaning of "directly supplied" is therefore critical; a narrow interpretation may allow the defendant to identify a circuit path that avoids infringement, while a broad one may favor the plaintiff.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation (Favoring Plaintiff): The claim specifies the input voltage is not supplied "as a power supply voltage." (’955 Patent, col. 12:62-64). This phrasing suggests the limitation is focused on the power rail providing operating energy to the controller. This aligns with the patent's overall objective of isolating the controller from power-line noise, potentially allowing for other types of connections (e.g., sense or signal lines) without violating the claim.
- Evidence for a Narrower Interpretation (Favoring Defendant): The term "directly" is not explicitly defined. A defendant could argue that any electrical path from the input voltage pin to the controller, even one with intervening passive components, constitutes a form of "direct" supply, or that the term is indefinite.
VI. Other Allegations
- Indirect Infringement: The complaint alleges inducement by asserting that Defendant provides datasheets, schematics, and other technical materials that instruct and encourage customers to implement the accused products in an infringing manner. (Compl. ¶77). It further alleges contributory infringement, stating the accused products are a material part of the claimed invention and are not staple articles of commerce suitable for substantial non-infringing use. (Compl. ¶78).
- Willful Infringement: Willfulness is alleged based on the theory that Defendant, as an active participant in the power management market, investigates competitor patent portfolios, including those of Japanese companies where the asserted patent originated, and therefore knew or should have known of the ’955 Patent. (Compl. ¶46).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of architectural mapping: does the highly integrated circuitry of the accused products, as represented by their functional block diagrams, contain a "controller" and "reference voltage source" that are powered by an internal linear regulator in the specific manner required by Claim 1? This will depend heavily on the court's construction of "controller."
- The case will also likely feature a significant evidentiary question regarding the negative limitation. A central dispute may be whether discovery reveals any power path from the primary input voltage to the accused controller that falls outside the patent's prohibition on being "directly supplied... as a power supply voltage," potentially creating a non-infringement defense.