SAN FRANCISCO (MarketWatch) -- Synaptics Inc. (SYNA) fell $3, or 14%, to $18.47 Friday after the touchpad-technology developer said its fourth-quarter earnings would likely be less than Wall Street estimates. Synaptics also said its revenue would be flat with its third quarter results of $56.7 million. Analysts surveyed by Thomson First Call had forecast Synaptics to post a fourth-quarter profit of 31 cents a share on $57 million in revenue. Synaptics officials said the company, which supplies components used in Apple Computer`s (AAPL) iPod music player, expects to see softness in its music player business in the current quarter. Other iPod component suppliers also retreated, with PortalPlayer Inc. (PLAY) down $1.58, or 9%, at $16; SigmaTel Inc. (SGTL) off by $2.75, or almost 11%, to trade at $24.96, and Seagate Technology (STX) , down 69 cents, or more than 3%, at $18.20.