Print PDF

“Circuit”-Plus-Function Is Not Means-Plus-Function

02-1569
June 17, 2004

Decision icon Decision

Last Month at the Federal Circuit - June/July 2004

Judges: Linn (author), Newman, and Schall

In Linear Technology Corp. v. Impala Linear Corp., No. 02-1569 (Fed. Cir. June 17, 2004), the Federal Circuit vacated the district court’s grant of SJ of noninfringement in favor of Maxim Integrated Products, Inc. (“Maxim”) after concluding that the district court had erred in construing certain claim limitations of U.S. Patent No. 5,481,178 (“the ‘178 patent”) owned by Linear Technology Corporation (“Linear”). The ‘178 patent relates to voltage regulators, which are designed to provide a predetermined and constant voltage output from a fluctuating input voltage source, such as a battery, to an energy consuming device. The Federal Circuit also vacated the district court’s grant of SJ of no contributory infringement or inducement with respect to certain claims of the ‘178 patent because Linear had raised genuine issues of material fact concerning direct infringement. Finally, the Federal Circuit affirmed the district court’s denial of Maxim’s motion for SJ that Ronald Vinsant was a joint inventor of the ‘178 patent.

On appeal, the Federal Circuit first reviewed the district court’s construction of the claim terms “circuit,” “vary the duty cycle,” and “simultaneously off.” The Court concluded that the district court had incorrectly construed the “circuit” and “circuitry” claim limitations of the ‘178 patent as means-plus-function limitations subject to 35 U.S.C. § 112, ¶ 6, even though these limitations recited only the functions of the circuits. Because none of the disputed limitations included the word “means,” the Federal Circuit held that the district court legally erred by failing to apply the rebuttable presumption that § 112, ¶ 6 does not apply. The Court looked at some technical dictionaries and concluded that the term “circuit” connotes structure. The Court ruled that “when the structure connoting term ‘circuit’ is coupled with a description of the circuit’s operation, sufficient structural meaning generally will be conveyed to persons of ordinary skill in the art, and § 112, ¶ 6 presumptively will not apply.”

The Federal Circuit also disagreed with the district court’s construction of “vary the duty cycle,” which was written in means-plus-function format. The district court had held that the pulse width modulation (“PWM”) circuits mentioned in the specification were not corresponding structure for this limitation because the term PWM is essentially generic and does not reference a specific structure. The Federal Circuit noted that although the expression “PWM circuit” does not reference a specific circuit structure, persons of skill in the art would understand that “PWM circuit” references a discrete class of circuit structures that perform known functions.

The Federal Circuit also found that the district court had erred in construing the “simultaneously off” limitations recited in certain claims of the ‘178 patent. Specifically, these limitations state: “to cause both switching transistors to be simultaneously OFF for a period of time.” The district court had construed these limitations as encompassing “the act of turning or causing both transistors to be off, not the state of being off, that occurs simultaneously.” The Federal Circuit disagreed, concluding that the ordinary and customary meaning of “simultaneously off,” in contextual relation to the “period of time” language of the claims, encompasses the simultaneous state of both switching transistors being disabled or held off. Thus, the Court concluded that “simultaneously off” limitations require that both switching transistors be held off or disabled for an overlapping period of time, not that they be turned off or disabled at the same instant.

The Federal Circuit next turned to the district court’s grant of SJ of no contributory infringement or inducement with respect to certain claims of the ‘178 patent. The Court reviewed all the record evidence and concluded that this evidence raised a genuine issue as to whether Maxim’s customers directly infringed, and hence, whether Maxim contributed to or induced infringement. It therefore vacated the district court’s grant of SJ of noninfringement.

Finally, the Federal Circuit addressed Maxim’s cross appeal. The Court noted that the parties disputed whether the district court had erred in finding that Ronald Vinsant’s claim of joint inventorship of the ‘178 patent was not corroborated and also in denying Maxim’s motion for SJ that Vinsant was a joint inventor of the ‘178 patent. The Court noted that because Maxim’s cross appeal is from a district court’s denial of its motion for SJ, it would not disturb that determination in the absence of an abuse of discretion. The Federal Circuit then reviewed the corroboration evidence and agreed with the district court’s assessment of that evidence. Specifically, the Court held that the district court had not abused its discretion in concluding that Vinsant’s inventorship claim was not corroborated.