CSR hits $6 parts cost for DSP-Bluetooth headset

In the world of Bluetooth-headset design, every cent of the BOM (bill of materials) counts. With that fact in mind, CSR has introduced single-chip devices with BOM figures of $5 and $6. The BlueVox2 headset costs $5, and the extra $1 adds DSP for active noise cancellation to remove ambient sounds from the microphone channel. The company’s Kalimba block adds the DSP function, with either single-microphone operation or dual-microphone channels; the second microphone is for ambient noise and adds just a few cents to the cost. The DSP code is in ROM, also lowering costs.

The chip operates to Bluetooth 2.1 EDR (enhanced data rate) and implements the company’s AuriStream codec for improved voice quality and lower power when both ends of the link can use it or autonegotiates 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 from Cambridge Consultants. A reference design is available; it includes not only complete layout and component information, but also a built and working example. Power demand is 11 to 14 mA at 3.7V, depending on the 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, according to the company. The non-DSP version has similar RF performance and power requirements of 6.5 to 8.5 mA.