Linear Technology Corp. v. Impala Linear Corp.

• Citation: 379 F.3d 1311
• Decision Date: 17 August 2004
• Docket Number: No. 02-1576.,No. 02-1569.,02-1569.,02-1576.
• Parties: LINEAR TECHNOLOGY CORPORATION, Plaintiff/Counterclaimant-Appellant, v. IMPALA LINEAR CORPORATION, Toyoda Automatic Loom Works, Ltd., and Analog Devices, Inc., Defendants, and Maxim Integrated Products, Inc., Defendant/Counterclaim Defendant-Cross Appellant, and Unitrode Corporation, Defendant, and Ronald Vinsant, Counterclaim Defendant-Appellee.
• Court: United States Courts of Appeals. United States Court of Appeals for the Federal Circuit

379 F.3d 1311

LINEAR TECHNOLOGY CORPORATION, Plaintiff/Counterclaimant-Appellant, v. IMPALA LINEAR CORPORATION, Toyoda Automatic Loom Works, Ltd., and Analog Devices, Inc., Defendants, and Maxim Integrated Products, Inc., Defendant/Counterclaim Defendant-Cross Appellant, and Unitrode Corporation, Defendant, and Ronald Vinsant, Counterclaim Defendant-Appellee.

No. 02-1569.

No. 02-1576.

United States Court of Appeals, Federal Circuit.

DECIDED: August 17, 2004.

Appeal from the United States District Court for the Northern District of California, Vaughn R. Walker, J.

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Alan H. Blankenheimer, Heller Ehrman White & McAuliffe LLP, of San Diego, CA, filed a combined petition for rehearing and rehearing en banc for defendant/counterclaim defendant-cross appellant, and counterclaim defendant-appellee. On the petition was Laura E. Underwood. Of counsel on the petition were Chad S. Campbell and Dan L. Bagatell, Brown & Bain, P.A., of Phoenix, AZ William K. West, Jr., Howrey Simon Arnold & White, LLP, of Washington, DC, filed a response to the petition for plaintiff/counterclaimant-appellant. With him on the response was David W. Long.

William P. Atkins, Pillsbury Winthrop LLP, of McLean, VA, filed an amicus curiae brief for Intel Corporation. With him on the brief was Evan Finkel, of Los Angeles, CA.

William K. West, Jr., Howrey Simon Arnold & White, LLP, of Washington, DC, argued for plaintiff/counterclaimant-appellant. With him on the brief were David W. Long, Jenny W. Chen, and Pamela S. Kane.

Alan H. Blankenheimer, Heller Ehrman White & McAuliffe LLP, of San Diego, CA, argued for defendant/counterclaim defendant-cross appellant, and counterclaim defendant-appellee. On the brief were Chad S. Campbell and Dan L. Bagatell, Brown & Bain, P.A., of Phoenix, AZ. Of counsel was Laura E. Underwood, Heller Ehrman White & McAuliffe LLP, of San Diego, CA.

Before NEWMAN, SCHALL, and LINN, Circuit Judges.

ORDER

A combined petition for panel rehearing and rehearing en banc was filed by Maxim Integrated Products, Inc. ("Maxim") and a response thereto was invited by the court and filed by Linear Technology Corporation ("Linear"). An amicus curiae brief was filed by Intel Corporation. Thereafter, these filings were referred to the merits panel that heard the appeal.

Upon consideration thereof,

IT IS ORDERED THAT:

(1) The Petition for Panel Rehearing is granted for the limited purpose of correcting this court's reporting of a portion of the district court's decision.

(2) The previous opinion of the court in this appeal, issued on June 17, 2004 and reported at 371 F.3d 1364, is withdrawn and the opinion attached to this order is substituted in its place.

(3) In all other respects, the Petition for Panel Rehearing is denied.

(4) The Petition for Rehearing En Banc is denied.

The mandate shall issue on August 24, 2004.

LINN, Circuit Judge.

A petition for panel rehearing was filed by Maxim and granted by the panel for the limited purpose of correcting this court's reporting of the district court's decision on Linear's motion for summary judgment that Vinsant was not an inventor of the '178 patent. This opinion replaces the court's original opinion in response to the petition for rehearing. The disposition of the appeal is unchanged.

Linear Technology Corporation ("Linear") appeals from a decision of the United States District Court for the Northern District of California, in Civil Action No. 98-CV-1727, granting summary judgment of non-infringement in favor of defendant Maxim Integrated Products, Inc. ("Maxim") with respect to Linear's U.S. Patent No. 5,481,178 ("the '178 patent"). Maxim conditionally cross-appeals the district court's entry of summary judgment that Ronald Vinsant was not an inventor of the '178 patent. Because the district court erred in construing the "circuit" and "circuitry," "vary the duty cycle," and "simultaneously off" claim limitations of the '178 patent, we vacate the judgment of non-infringement and remand for further consideration. Because genuine issues of material fact have been raised concerning Maxim's contributory infringement or inducement, we vacate the district court's summary judgment of no contributory infringement or inducement of the current reversal method claims of the '178 patent. Because Maxim failed to raise a genuine issue of material fact, the matter of inventorship was amenable to determination on summary judgment on the undisputed factual premises. On these premises, the district court correctly held that Vinsant was not a joint inventor of the '178 patent.

I. BACKGROUND

This appeal 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, called a "load." Voltage regulators of the "switching" type use transistors, which are turned on and off like switches, to control the electrical power supplied by a power source. '178 patent, col. 1, ll. 20-24. Switching voltage regulators transmit power to the load in discrete current pulses. Id. at col. 1, ll. 27-28. To ensure a steady flow of current pulses, control circuitry is used to turn the transistors on and off. Id. at col. 1, ll. 31-33. Selectively turning the transistors off advantageously reduces the power dissipated in the regulator itself, yielding higher efficiencies for switching voltage regulators as compared to other regulator designs. See id. at col. 1, ll. 39-41; id. at col. 1, ll. 48-50. The '178 patent discloses a "sleep mode" where both switching transistors are turned off to additionally reduce the power consumed by the regulator itself to further improve the regulator's efficiency. Id. at col. 5, ll. 59-66. Also disclosed is a current reversal prevention mode where the regulator prevents the reverse flow of electrical current to forestall power from being drained from the load. Id. at col. 14, ll. 1-10.

Independent claim 1 is representative of a "sleep mode" claim of the '178 patent, and is reproduced below with the disputed limitations highlighted:

1. A circuit for controlling a switching voltage regulator, the regulator having (1) a switch circuit coupled to receive an input voltage and including a pair of synchronously switched switching transistors and (2) an output circuit including an output terminal and an output capacitor coupled thereto for supplying current at a regulated voltage to a load, the control circuit comprising:

a first circuit for monitoring a signal from the output terminal to generate a first feedback signal;

a second circuit for generating a first control signal during a first state of circuit operation, the first control signal being responsive to the first feedback signal to vary the duty cycle of the switching transistors to maintain the output terminal at the regulated voltage; and

a third circuit for generating a second control signal during a second state of circuit operation to cause both switching transistors to be simultaneously OFF for a period of time if a sensed condition of the regulator indicates that the current supplied to the load falls below a threshold fraction of maximum rated output current for the regulator, whereby operating efficiency of the regulator at low output current levels is improved.

Id. at col. 16, ll. 34-57 (emphases added). Asserted independent claims 34, 41, 55, and 57 are also "sleep mode" claims.

Independent claim 51 is exemplary of a current reversal prevention mode claim, and is reproduced below:

51. A method for controlling a switching voltage regulator, the regulator having (1) a switch circuit coupled to receive an input voltage and including a pair of synchronously switched switching transistors and (2) an output circuit including an output terminal and an output inductor coupled thereto for supplying current at a regulated voltage to a load, the method comprising the steps of:

(a) monitoring a signal from the output terminal to generate a first feedback signal;

(b) varying the duty cycle of the switching transistors in response to the first feedback signal to maintain the output terminal at the regulated voltage during a first state of circuit operation, wherein the current to the load has a polarity; and

(c) maintaining one of said switching transistors OFF for a period of time following the first state of circuit operation to de-couple the output circuit from ground during the period of time so as to prevent the current to the load from reversing polarity.

Id. at col. 21, ll. 9-27 (emphasis added).

In 1997, Linear sued Maxim; Impala Linear Corporation ("Impala"); Toyoda Automatic Loom Works, Ltd. ("Toyoda"); Analog Devices, Inc. ("Analog"); and Unitrode Corporation ("Unitrode"), all manufacturers of switching voltage regulators, for infringement of claims 1-3, 31-35, 41, and 55-57 (the sleep mode claims) and claims 44-48 and 51-54 (the current reversal claims) of the '178 patent. On June 9, 1999, the district court issued a claim construction order construing all asserted claims of the '178 patent. Linear Tech. Corp. v. Impala Linear Corp., No. C-98-1727-FMS (N.D. Cal. June 9, 1999) ("Claim Construction Order"). On September 21, 2001, a different district court judge issued an order granting summary judgment of non-infringement in favor of Maxim and granting Linear's motion for summary judgment that Vinsant was not an inventor of the '178 patent. Linear Tech. Corp. v. Impala Linear Corp., No. C-98-1727-VRW (N.D.Cal. Sep. 21, 2001) ("Summary Judgment Order"). Some of the original claim constructions in the Claim Construction Order were modified in the subsequent Summary Judgment Order. On October 26, 2001, the district court entered final judgments under Rule 54(b) concerning Unitrode, Maxim, and Vinsant and, given the interest of Analog in the claim constructions, issued an Order certifying an interlocutory appeal of the claim...