In its action, filed in U.S. District Court in Texas, Microtune charges that Broadcom's BCM 3415 tuner chip violates a patent that covers putting a TV tuner on a single chip.
Broadcom spokesman Bill Blanning said the company had not had a chance to review the complaint in detail but said it appears to be without merit.
"It appears to be frivolous litigation intended to prevent the rollout of our superior, competitive silicon tuner product," Blanning said.
Plano, Texas-based Microtune said in a statement it is seeking monetary damages resulting from the alleged infringement, as well as an injunction against further infringement.
Microtune President James Fontaine told CNET News.com said the suit was based on a review of the information that Broadcom has made public about its tuner chip. Fontaine said the company has not actually examined the chip itself.
"We've invested pretty heavily in the intellectual property," Fontaine said. "We really believe we need to defend this."
Microtune got its single-chip tuner patent in April 1998 and introduced its first chip in January 1999. The chip has been used in products for about a year, Fontaine said.
The suit comes a day after Broadcom reported fourth-quarter earnings that edged past Wall Street estimates.
Shares of Broadcom surged in after-hours trading Tuesday and opened higher Wednesday but then retreated. Broadcom shares closed down $8.50, or 6 percent, at $124.94.
The intellectual-property dispute is not the first for Broadcom, which settled a trade-secret dispute in November that stemmed from Broadcom's hiring of several former Intel workers. Intel still has a separate patent infringement suit against Broadcom in U.S. District Court in Delaware.