PA Semi founder and CEO, Dan Dobberpuhl, has apparently left Apple to join a Silicon Valley startup company founded by other former PA Semi employees. PA Semi is a chip design company that Apple purchased in 2008.

When Apple bought PA Semi, CEO Steve Jobs said it would use the company to design system-on-chip products for the iPhone and iPod. Mr. Dobberpuhl was kept on to run the design team.

Exactly when Mr, Dobberpuhl left Apple, however, is a bit of a mystery, according to CNET. Apple isn’t talking about his departure, but some industry sources claim he left last fall. Exactly where Mr. Dobberpuhl landed is a bit of a mystery, too, although sources think Agnilux — the company founded by other former PA Semi employees — is the most likely place.

Other former PA Semi employees have left Apple, too, taking their chip design expertise with them. Linley Gwennap, president and principal analyst of The Linley Group, said that Mr. Dobberpuhl was “[The] leader of the team, and one of the guys that was driving the whole thing. But those guys are start-up kind of people, and within the structure of Apple, they may [have been] chafing.”