Design Article
Bluetooth making good on price points
David Carey
3/1/2004 9:46 AM EST
Six years after a much-publicized rollout promising inexpensive, fiddle-free wireless, it seems Bluetooth has met its original cost objective. Two USB adapters help reveal the state of Bluetooth ASIC integration and highlight the varying paths taken in chip partitioning. But while the Bluetooth ICs differ, they are similar in selecting CMOS to create monolithic RF, mixed-signal and mixed-function designs.
The EPoX BT-DG02 is the larger of the plug-in adapters. Centered on the Cambridge Silicon Radio BC212015, the EPoX design places all components on one side of a four-layer circuit board. The CSR part integrates transceiver, baseband processor and memory on one chip, with memory augmented by 512 kbytes of Silicon Storage Technology E2PROM. Two regulators supply voltages to the Cambridge and SST parts and an STMicroelectronics silicon-based ESD-protection chip guards against static damage from the USB interface.
But silicon alone can rarely complete a radio system; resistors, capacitors and inductors make up most of the 54 components in the EPoX design. A crystal oscillator, chip-form balun and RF antenna filter are also needed, along with a TriCome surface-mount antenna, which enables the 10-meter range of the EPoX adapter.
The smaller D-Link DBT-120 also has 54 components, but double-sided part placement raises component density and drops board area. D-Link's design differs from the EPoX in chip selection, too, tapping Broadcom's BCM2033 Bluetooth chip as the core device. Like the CSR part, the BCM2033 integrates transceiver and baseband but goes further by integrating system memory. Only Microchip's diminutive, 128-byte E2PROM supplements the BCM2033's on-chip storage. Micrel supplies the D-Link adapter's lone voltage regulator and a set of discrete components similar to the EPoX approach rounds out the design.
While possibly integrated on the Broadcom part, no standalone devices for ESD protection are present. A small, multilayer-ceramic SMT antenna (manufacturer unknown) achieves the same claimed radio range as the EpoX design: 10 meters.
Despite differences in ASIC implementation, both adapters had an estimated cost-of-goods sold in the $7 range. Excluding overhead tied to the USB adapter format, core Bluetooth solutions now stand near the target cost of $5.
New standards take time. Arguably, Bluetooth solutions have just entered the cost realm where the technology's uptake can build in a big way. But just as important as cost is usability, which will be key to Bluetooth's potential for home-run success.
David Carey is president of Portelligent (Austin, Texas; www.teardown.com), which produces teardown reports and related industry research on wireless, mobile and personal electronics.
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