Microchip designer ARM has announced that Sir John Buchanan is stepping down as chairman due to a medical condition.

He will be replaced by Stuart Chambers, who joins the board today as chairman designate, and will take over fully on 1 March 2014.

Chambers is chairman of global consumer packaging company Rexam and a non-executive director of supermarket chain Tesco. He was group CEO of Nippon Sheet Glass Group until 2009, and prior to the glass industry, he held a number of senior roles at confectionary manufacturer Mars and oil and gas company Royal Dutch Shell.

"Due to the medical uncertainties it is right that we should secure the chairman succession at this time," said Buchanan.

The outgoing chairman has served on the board over the last two years. He was the former deputy chair of Vodafone and is also the outgoing chairman of Smith & Nephew, the medical equipment manufacturer. He will retire on 1 May 2014.

Cambridge-based ARM is one of the UK's technology darlings, buoyed by the use of its chips in Apple mobile devices. Its long-serving CEO, Warren East, who joined the company in 1994, retired from his role last year, and was succeeded by former president of ARM, Simon Segars.