Judges: Mayer, Lourie, Schall (author)

[Appealed from ITC]

In Linear Technology Corp. v. International Trade Commission, Nos. 08-1117, -1165 (Fed. Cir. May 21, 2009), the Federal Circuit agreed with the ITC’s claim construction of the asserted claims in U.S. Patent No. 6,580,258 (“the ’258 patent”) in all respects except one. The Court affirmed the ITC’s finding that one voltage regulator product by Advanced Analogic Technologies, Inc. (“AATI”) infringed three “sleep mode” claims of the ’258 patent and affirmed the finding that those claims were not anticipated. The Federal Circuit also affirmed that two other voltage regulators did not infringe two of the three “sleep mode” claims, but vacated and remanded the noninfringement finding with respect to the third claim. Further, the Court reversed the finding that a fourth product did not infringe the three “sleep mode” claims. Finally, the Court vacated and remanded the finding that two of the products did not infringe the asserted “reverse current” claim, as well as the finding that this claim was anticipated.

Linear Technology Corporation (“Linear”) is the owner of the ’258 patent, which is a continuation of U.S. Patent No. 5,481,178 (“the ’178 patent”). The ’258 patent is directed to achieving higher efficiency in switching voltage regulators through two improvements: use of a “sleep mode” and prevention of “reverse current” situations.

Linear filed a complaint at the ITC alleging that AATI imported and/or sold for importation numerous electronic voltage regulators that infringe the ’258 patent. The parties agreed to designate four representative regulators: AAT1143, AAT1146, AAT1151, and AAT1265. Linear alleged that all four products infringed claims 2, 3, and 34 of the ’258 patent, which cover an apparatus and method for implementing a “sleep mode” operation. Linear further alleged that two products (AAT1143 and AAT1146) infringed claim 35 of the ’258 patent, which covers a circuit involving “reverse current” protection. On review of an ALJ’s finding that AATI did not violate section 337, the ITC modified the ALJ’s claim construction and findings, holding that (1) the AAT1143 infringed the three “sleep mode” claims; (2) the other three regulators did not infringe either the “sleep mode” or “reverse current” claims; (3) the “sleep mode” claims were not anticipated by a reference entitled “Application Note 35—Step Down Switching Regulators” (“AN35”); and (4) the “reverse current” claim was anticipated by the MAX782 product.

The Federal Circuit first considered the claim constructions of five contested limitations. With respect to the first limitation, “switch . . . including a pair of synchronously switched switching transistors,” the Court found no error because the construction was identical to the express definition within the specification of the ’258 patent. Regarding the second limitation, the Court held that the terms “second circuit” and “third circuit” were correctly construed to not require entirely separate and distinct circuits. The Court noted that there was nothing in the claim language or specification that supported narrowly construing the claim terms. The Court explained that the circuits must only perform their stated functions and that, in fact, the ’258 patent expressly disclosed, at least in Figure 2, that the “second” and “third” circuits can share components. AATI contended that the correct construction required that the additional component must participate in performing the claimed function. The Federal Circuit stated that such a construction was unnecessary because the claim language already required the components to aid in the circuit’s function.

With respect to the third limitation, the Federal Circuit affirmed the ITC’s construction of “a second control signal . . . to cause both transistors to be OFF.” AATI argued that the limitation required causation without the intervention of other signals or components. The Court disagreed, reasoning that the specification did not indicate that it required direct causation. The Court noted that the direct causation would be nearly unworkable to articulate or ascertain and that such a requirement would allow an accused infringer to evade infringement by merely identifying an intermediary signal or component that allegedly breaks the chain of causation. Further, the Court noted that AATI’s construction would be contrary to the specification, which disclosed components that are located between the generation of the second control signal and the switching transistors. In construing the nearly identical but more restrictive claim limitations of the parent ’178 patent, the Court found that “to cause both switching transistors to be simultaneously OFF for a period of time” should not be construed to include a narrow causation requirement. Finally, with respect to the ITC’s finding that the limitation did not require the second control signal to be entirely distinct from the first control signal, the Court noted that the specification supported this construction.

The Federal Circuit then affirmed the ITC’s construction of “first state of circuit operation” and “second state of circuit operation.” AATI argued that the “first state” should occur at high load currents while the “second state” should only occur at low load currents. The Court disagreed, noting that, while the ’258 patent provides examples and embodiments in line with AATI’s proposed construction, there was no clear intent to limit the claim scope. Further, the ’258 patent disclosed situations contrary to the suggested construction, for example, operating in the “first state” at low load currents. The Court also stated that the amendments and statements made in the prosecution of the parent ’178 patent were plainly different from AATI’s proposed construction, and thus did not show a clear and unmistakable disavowal of claim scope. The Court then stated that the remainder of the claim language that modified the disputed elements clearly described the terms.

Finally, the Federal Circuit found that the ITC had effectively construed the “monitoring the current to the load” limitation of claim 35 during its infringement analysis, even though it did not issue an explicit claim construction. The Court held that the construction, which excluded indirectly monitoring current through the measurement of voltage, was improperly narrow. The Court noted that the claim did not state “directly” monitoring current, and that the ’258 patent discloses monitoring current both directly and indirectly. Accordingly, the Court held that this limitation could be satisfied by monitoring voltage to indirectly monitor current.

The Federal Circuit next considered infringement by AATI’s four voltage regulators with respect to the “sleep mode” claims. First, the Court affirmed the infringement of all three “sleep mode” claims by the AAT1143 device. With respect to circuit claims 2 and 3, the Court noted there was substantial evidence, including circuit schematics, graphs of the device in operation, and explanatory expert testimony, that the device infringed. Further, AATI’s arguments focused on several claim constructions that the Court had rejected. With respect to method claim 34, the Court rejected AATI’s argument that there was not substantial evidence that the device actually practiced the claimed method, pointing to testimony and documentation that AATI tested all of the accused products and generated voltage output graphs.

Second, the Federal Circuit reversed the ITC and found that the AAT1146 device infringed the circuit claims. The Court noted that the AAT1146 was nearly identical to AAT1143, which infringed the same claims. The Court found that one of the only apparent differences between the devices (i.e., that the AAT1146 was capable of switching two transistors at high frequency) was irrelevant to the claims. With respect to method claim 34, the Court again reversed the ITC and found infringement, citing various evidence and noting that the ITC simply decided, without identifying a missing claim limitation, that the AAT1146 did not infringe.

Finally, the Federal Circuit affirmed that neither the AAT1151 nor the AAT1265 infringed circuit claims 2 and 3 because neither device met the “third circuit” limitation. The Court explained that, not only did Linear fail to explain how certain circuits allegedly met the claim requirements, there was also substantial evidence that those circuits were operably different from the circuitry in the infringing AAT1143 and AAT1146 devices in marked ways. However, with respect to method claim 34, the Court vacated and remanded the ITC’s finding of noninfringement. Noting that the method claim was broader than circuit claims 2 and 3, the Court noted that the ITC’s finding that the AAT1265 did not infringe claim 34 was based solely on one statement that was wholly contradictory. The Court further noted that the ITC did not provide any reason why the AAT1151 did not infringe claim 34.

The Federal Circuit then considered the validity of the “sleep mode” claims. The ITC found claims 2, 3, and 34 valid because the AN35 reference did not disclose the second switching transistor required by the claims. AATI argued that the ITC ignored Appendices A and D, which were allegedly part of AN35 and describe adding a second synchronous transistor. The Federal Circuit, however, disagreed. The Court noted that, even considering Appendices A and D in combination with the AN35 disclosure, there was still substantial evidence that the claims were not anticipated. Notably, there was no explanation as to how substituting the components would necessarily result in the exact operational circuit.

Finally, the Federal Circuit considered the infringement and validity of the “reverse current” claim. Noting that the ITC’s finding that the AAT1143 and AAT1146 devices did not infringe claim 35 had been based on an improper claim construction, the Court vacated and remanded. Similarly, with respect to the validity of claim 35, the Federal Circuit held that the ITC’s incorrect claim construction infected its validity analysis and remanded.