DCT
1:19-cv-01111
Aido LLC v. STMicroelectronics Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Aido LLC (Texas)
- Defendant: STMicroelectronics, Inc. (Delaware)
- Plaintiff’s Counsel: Stamoulis & Weinblatt LLC
- Case Identification: 1:19-cv-01111, D. Del., 06/17/2019
- Venue Allegations: Venue is alleged to be proper in the District of Delaware because Defendant, a Delaware corporation, conducts substantial business in the forum.
- Core Dispute: Plaintiff alleges that Defendant’s class-D audio amplifier integrated circuits infringe a patent related to a technique for reducing signal distortion in switching amplifiers.
- Technical Context: The technology concerns high-efficiency class-D switching amplifiers, which are critical components in modern audio systems for converting digital signals into power to drive speakers.
- Key Procedural History: The complaint does not mention any prior litigation, Inter Partes Review (IPR) proceedings, or licensing history related to the patent-in-suit.
Case Timeline
| Date | Event |
|---|---|
| 2000-08-28 | U.S. Patent No. 6,937,090 Priority Date |
| 2005-08-30 | U.S. Patent No. 6,937,090 Issued |
| 2019-06-17 | Complaint Filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 6,937,090 - "Charge Injection Reduction Technique in Single and Multi-Reference Switching Amplifiers"
- Patent Identification: U.S. Patent No. 6,937,090, "Charge Injection Reduction Technique in Single and Multi-Reference Switching Amplifiers," issued August 30, 2005.
The Invention Explained
- Problem Addressed: In high-accuracy switching amplifiers, the control signals used to turn switches on and off can "inject" a small, unwanted electrical charge into the output signal. The patent’s background section states this "parasitic effect" can cause significant signal distortion, particularly in bipolar amplifier designs. (’090 Patent, col. 1:17-34).
- The Patented Solution: The invention proposes a method to counteract this distortion. It involves intentionally adding a "minimum pulse width of the same polarity" to the control signals for the switching devices on both sides of a differential output. (’090 Patent, Abstract). By injecting a similar, correlated error pulse into both outputs at the same time, the unwanted charge presents as a "null common-mode output," which is effectively canceled out when the differential signal is processed, thereby preserving the accuracy of the final analog output. (’090 Patent, col. 1:36-44).
- Technical Importance: This technique addresses a fundamental source of distortion in a widely used class of amplifiers, offering a method to improve audio fidelity and signal accuracy without requiring more complex or expensive components. (’090 Patent, col. 1:11-16).
Key Claims at a Glance
- The complaint asserts at least independent claim 1. (Compl. ¶10).
- Independent Claim 1: The essential elements are:
- In a switching amplifier with gated switches controlled by a pulse-width modulated (PWM) input signal,
- adding a minimum pulse width of the same polarity to a pair of switching devices simultaneously, one on either side of the load,
- in order to null the common-mode output presented to the load.
- The complaint does not explicitly reserve the right to assert other claims but notes infringement of "one or more claims." (Compl. ¶11).
III. The Accused Instrumentality
Product Identification
- The accused instrumentality is Defendant’s TDA7491HV integrated circuit. (Compl. ¶10).
Functionality and Market Context
- The complaint identifies the TDA7491HV as a class-D audio amplifier that uses a unipolar pulse width modulation (PWM) scheme to power a speaker load. (Compl. ¶12-13). It is alleged to employ differential inputs to minimize common-mode noise and features a modulation scheme where the outputs (OUTP and OUTN) are "in the same phase almost overlapped when the input is zero." (Compl. ¶13-14). The complaint includes a datasheet block diagram, Figure 1, which provides an internal block diagram of one channel of the accused device. (Compl. p. 3).
- The complaint alleges the device is a switching amplifier used for audio applications. (Compl. ¶12).
IV. Analysis of Infringement Allegations
'090 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| In a switching amplifier of the type wherein one or more references are coupled to a load through gated switches controlled by a pulse-width modulated input signal, the improvement comprising: | The Accused Device is a class-D audio amplifier that powers a speaker load through switches controlled by a PWM input signal generator. | ¶12 | col. 2:32-35 |
| adding a minimum pulse width of the same polarity to a pair of switching devices simultaneously, one on either side of the load, | The Accused Device allegedly uses a PWM scheme that adds a minimum pulse width. The complaint alleges this results in differential outputs (OUTP and OUTN) that are in the "same phase or 'polarity'". | ¶13 | col. 2:36-39 |
| to null the common-mode output presented to the load. | The Accused Device allegedly uses differential input to "minimize the common mode noise," which the complaint equates to the claimed function of nulling the common-mode output. | ¶14 | col. 2:39-40 |
Identified Points of Contention
- Scope Questions: The complaint quotes a portion of the accused device’s datasheet stating that "a short delay is introduced between these two outputs in order to avoid the BTL output switching simultaneously." (Compl. ¶13). This raises the question of whether the accused device’s operation can meet the claim limitation requiring the addition of pulses "simultaneously".
- Technical Questions: Does the "unipolar pulse width modulation (PWM)" scheme described in the datasheet for the accused device (Compl. ¶13) perform the same function in the same way as the claimed "adding a minimum pulse width ... to null the common-mode output"? A central issue may be whether the accused modulation scheme, allegedly used to reduce current ripple, is technically equivalent to the patent’s specific technique for canceling charge-injection error. The complaint includes a timing diagram, Figure 55, to illustrate the unipolar PWM output waveforms of the accused device. (Compl. p. 5).
V. Key Claim Terms for Construction
The Term: "simultaneously"
- Context and Importance: This term is critical because the complaint itself provides evidence from the accused product's datasheet that a "short delay is introduced... to avoid" simultaneous switching. (Compl. ¶13). The infringement analysis will depend heavily on whether the term allows for any non-zero delay between the application of pulses to the two switches.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: A party could argue that in the context of physical circuits, "simultaneously" does not require perfect, instantaneous alignment but rather a degree of correlation sufficient to achieve the claimed functional result of nulling the common-mode output.
- Evidence for a Narrower Interpretation: The plain and ordinary meaning of the term implies occurring at the same instant. The patent specification does not appear to provide an alternative definition, potentially supporting a strict temporal interpretation.
The Term: "adding a minimum pulse width"
- Context and Importance: Practitioners may focus on this term because it defines the core inventive action. The dispute may turn on whether the accused device performs an affirmative step of "adding" a pulse, as the claim language suggests, or whether the presence of a minimum pulse is merely an inherent characteristic of its "unipolar PWM" modulation scheme. (Compl. ¶13).
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent does not specify a particular circuit or algorithm for "adding" the pulse, which a party could argue supports construing the term to cover any method that results in a minimum pulse being present to achieve the claimed function.
- Evidence for a Narrower Interpretation: The claim is written as a method improvement ("the improvement comprising: adding..."), and the Summary of the Invention describes "a method of adding a minimum pulse width." (’090 Patent, col. 1:36-37). This language may support an interpretation that requires a distinct, additive step rather than an inherent property of a modulation technique.
VI. Other Allegations
- Indirect Infringement: The complaint does not contain specific allegations of induced or contributory infringement. It focuses on direct infringement by "making, using, importing, offering for sale, and/or selling" the accused device, including through Defendant's "internal use and testing." (Compl. ¶10-11).
- Willful Infringement: The complaint does not allege facts to support pre-suit or post-suit knowledge of the patent or infringement. A request for a declaration that the case is "exceptional" under 35 U.S.C. § 285 is included in the prayer for relief, but the factual allegations in the body of the complaint do not explicitly plead willfulness. (Compl. p. 7).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of definitional scope: can the claim term "simultaneously" be construed to read on the operation of the accused device, which its own datasheet describes as implementing a "short delay" specifically "to avoid" simultaneous switching?
- A key technical question will be one of functional equivalence: does the accused product’s "unipolar PWM" scheme, which the datasheet presents as a method for reducing current ripple, constitute the specific inventive act of "adding a minimum pulse width ... to null the common-mode output" for the purpose of correcting charge-injection error, as taught by the '090 patent?