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CSR hits $6 parts-cost for DSP Bluetooth headset

Dual-microphone design with noise cancellation improves quality in low-cost designs

In the world of Bluetooth headset design, every cent of bill-of-materials counts; CSR has introduced its latest single chip solutions with BoM figures of $5 and $6 – the e-BoM, or cost of all the electronic components. $5 is for the BlueVox2, and the extra $1 adds DSP for active noise cancellation to remove ambient sounds from the microphone channel. CSR’s own Kalimba block adds the DSP function, with either single-microphone operation or dual microphone channels, the second one being for ambient noise, at an added cost of a few more cents. DSP code is in ROM for lower costs. The chip operates to Bluetooth 2.1 plus EDR and will implement CSR’s own Auristream codec for improved voice quality and lower power when both ends of the link can use it, or will auto-negotiate to fall back to a standard codec if not. Power management including battery charging is on-chip; the Bluetooth core is CSR’s Bluecore5 block and the control processor is an XAP2++ RISC core (Cambridge Consultants). CSRT is selling a reference design that not only includes complete layout and component information, but provides a built-and-working example. Power demand is 11-14 mA at 3.7V, depending on codec in use. Transmitter power is +8 dBm and receiver sensitivity is -90 dBm: these figures provide greater link robustness and avoid cross-body signal-loss dropouts, CSR says. The non-DSP version has similar RF performance and power requirements of 6.5-8.5 mA.