The Wisconsin Alumni Research Foundation, the patent licensing arm of the University of Wisconsin-Madison, said the verdict was important to guard its inventions from unauthorised use.

The jury had earlier decided that Apple incorporated patented microchip technology into some iPhones and iPads without permission.

Apple said it would appeal.

The company declined to comment further.

The amount was less than the foundation had claimed. It had originally sought as much as $862m.

The sum was lower in part because the judge ruled that Apple had not wilfully infringed the patent.

University of Wisconsin-Madison computer sciences professor Gurindar Sohi, one of the inventors of the microchip technology - designed to boost the performance of computer processors - was in the federal court in Madison, Wisconsin, for the decision.

"For Dr Sohi, I hope you felt that your invention was vindicated,'' US District Judge William Conley said.

'Seminal work'

Carl Gulbrandsen, managing director of the Wisconsin Alumni Research Foundation, said: "This is a case where the hard work of our university researchers and the integrity of patenting and licensing discoveries has prevailed.

"The jury recognised the seminal computer processing work that took place on our campus.''

The case relates to use of the technology in the iPhone 5s, 6 and 6 Plus - but an additional lawsuit making the same claim against Apple's newest models, the 6S and 6S Plus, has also been filed.

The University of Wisconsin sued Intel over the same patent in 2008. That case was settled out of court for an undisclosed sum.

Despite recent well-publicised truces between some big tech firms, fierce patent battles are still being fought in courts globally.

A judge recently threw out claims by graphic card specialist Nvidia that Samsung and others had infringed three of its patents.

Apple's annual revenue in 2014 was $182bn.

(BBC)