CSR has introduced a combined Bluetooth and audio processor chip, claiming it can stretch phone battery life to 100 hours in MP3 playback.

The Cambridge-based firm is already the major global supplier of Bluetooth transceivers for phones and headsets, and is seeking to bring more phone functions on to its silicon.

The dual-function chip is called MusiCore1.

"Handset makers using MusiCore1 can, for the first time, have stereo audio along with fully featured Bluetooth on a single chip," said CSR. "It saves 75 per cent of the cost of an audio processor, over 36mm² of space, and enables 100 hours of music playback."

Increased playback time comes from off-loading MP3 decode from one of the phone's large processors onto CSR's own 24bit 64Mips Kalimba DSP.

"End-users are demanding MP3 as a function in phones but currently not using it because decoding MP3 files consumes too much power," said Matthew Philips, v-p at CSR's handset business unit.

CSR is claiming 5.25mW for MP3 file decode, compared to the 80mW for the phone's CPU. The 100 hour figure is based on an 800mAh battery. "A typical dedicated MP3 player offers 24 hours," it said.

The chip includes a headphone driver for plug-in walkman-style headphones and can also directly feed Bluetooth headphones through the on-chip transceiver.

Formats including MP3, AAC, AAC+, WMA and SBC can be handled.

Power consumption is: 21.45mW for wired headphones from MP3 and WMA sources, 25.20mW for MP3 playback through MP3-supporting Bluetooth headphones, and 34.65mW for Bluetooth headphones using SBC including transcoding from MP3.

The Bluetooth transceiver supports v2.1 + EDR Bluetooth in its day job working with the rest of the phone, as well as CSR's own low (40ms) latency FastStream technology "that ensures there are no lip-synch issues when a phone is used for watching videos and is connected to Bluetooth headphones", claimed the firm. "Competing Bluetooth solutions have a latency of up to 200ms, which restricts their application for gaming, video or mobile TV."

Signal to noise ratio for wired playback is 95dB.

See also: Electronics Weekly's Focus on Bluetooth, a roundup of content related to the near-range wireless networking technology