Electronic Design

Highly Integrated Bluetooth IC Simplifies Design

Placing all RF, analog, and baseband functions on one chip expedites applications development.

Time-to-market will be more important than ever in the highly competitive Bluetooth applications market. Zeevo Inc. (formerly Telencomm Inc.) now gives you a chance to be early—maybe even first—with your Bluetooth-enabled product. Zeevo offers a complete solution with its new TC2000 single-chip transceiver and interface, which includes a full software development system and support.

The epitome of Bluetooth solutions is, of course, the single chip that does everything. The term "single chip" has different meanings for different vendors. To many, it means a one-chip RF transceiver. To make a complete Bluetooth product, however, you still need the baseband circuits in at least one other chip. Zeevo's product has the RF transceiver and the baseband circuits with interfaces on one chip.

The primary benefit of the Zeevo TC2000 chip over its competition is that it incorporates all the RF input/output circuits (impedance matching, baluns, switches, etc.), thereby eliminating many external components as well as the need for RF expertise in applying the chip. Digital designers and others lacking RF design expertise can employ this "digital looking" chip.

Built on a 0.18-µm CMOS chip are the radio, link controller, baseband controller, and interfaces (Fig. 1). The RF input/output filters and matching networks, although not physically located on-chip, are implemented with transmission lines and embedded into the package. This hybrid approach solves the problem of not being able to put some critical RF filter circuits in silicon. The result is still a single-package solution. The only external components required are a 12-MHz crystal, four capacitors, a resistor, and the antenna.

In the receiver section, the input from the single-lead antenna is coupled to the low-noise amplifier via the matching networks and a transmit/receive switch. The amplifier gives the receiver a sensitivity of greater than −80 dBm at the antenna input. I and Q mixers downconvert the signal directly to baseband. This direct-conversion approach eliminates any external SAW IF filters (Fig. 2).

Upconverting the baseband to an IF of 1.5 MHz eliminates the dc offset and other problems normally associated with direct-conversion receivers. This clever technique eliminates the need for two analog-to-digital converters (ADCs) and related circuitry. IF filtering is analog, and demodulation is accomplished digitally.

The signal is converted to digital form with a single ADC and then demodulated. After forward error correction (FEC), the data is de-whitened or descrambled. A cyclical redundancy check (CRC) operation is performed before sending the signal to the link manager and the baseband section.

In the transmitter section, the baseband digital data is used to produce the CRC. Then, the signal is whitened or scrambled. This process helps randomize the data to eliminate continuous patterns of ones and zeroes, thereby reducing the dc offset problem at the receiver. Next, FEC takes place, the output is converted to analog form, and the GFSK signal is produced. This is upconverted to the output frequency. The synthesizer is a traditional PLL with a single voltage-controlled oscillator at the channel frequency that's shared with the receiver.

An integrated power amplifier provides either a Class 2 or 3 power-level output. The output signal is coupled to the antenna via the matching network and switch. Also, the power-amplifier output may drive an external power amplifier for Class 1 operation. A control pin is provided on-chip to manage the output power.

The baseband section of the chip incorporates an ARM7TDMI processor, 64 kbytes of SRAM, 8 kbytes of boot ROM, and 4 Mbits of internal flash memory. Four DMA units associated with the processor handle all data movement, freeing the processor for other functions. Only about half of the processor's MIPS capability and half of the 4-Mbit flash are used for Bluetooth operations, leaving plenty of capability for the user to exploit for the application.

The baseband section also includes a variety of interfaces (USB 1.1 and UART are two among them), eight general-purpose input/output lines, and a PCM audio-codec interface for voice.

The TC2000 complies with the Bluetooth standard 1.0b. Furthermore, it meets the specifications for the version 1.1 standard, which is available but not yet ratified.

In addition to fulfilling Bluetooth specifications, the TC2000 supports all of the advanced features. Not all chips have this capability. The TC2000 can handle point-to-point and point-to-multipoint operation with up to seven slaves. It accommodates up to four Piconets and scatternets. Plus, it has a master/slave switch for printer applications. The full encryption feature of Bluetooth is implemented. The length of the encryption key can be varied in 8-bit increments from 0 to 128 bits. (For more information on Bluetooth, see "A Low-Power, Frequency-Hopping System," p. 98.)

Furthermore, the Zeevo chip has a unique 2x or 4x turbo mode that helps speed up the data transfers. Presently, the maximum Bluetooth speed is 723 kbits/s. With the Zeevo chip's proprietary turbo mode, a special compression/decompression algorithm allows data rates up to 3 Mbits/s.

When two Zeevo Bluetooth-enabled products encounter one another, they automatically switch to the turbo mode, using the higher data rate. The standard rate prevails when a Zeevo chip talks to a non-Zeevo product.

Finally, the TC2000 is housed in a low-temperature co-fired ceramic (LTCC) package that measures 9.85 by 11.85 mm. Contained within it are the input filters and baluns. A built-in RF shield protects the entire package. The pin-out is a 0.8-mm on-center ball-grid-array (BGA).

Two versions of this package are available. The TC2000P-4 has 4 Mbytes of on-chip flash and 65 balls, while the TC2000M-E requires an external flash memory and has 123 balls. The circuit operates from a 3.3-V supply.

When using the Zeevo chip, developing a Bluetooth-enabled product is really more of a software project than a hardware project. The software Zeevo provides includes the Bluetooth lower layer stack with host controller interface (HCI), which resides in flash. Additionally, the company offers both the upper and lower Bluetooth stacks in object or source code, as well as full support for all 1.0b profiles. The profiles define how the Bluetooth device works in common applications, including serial ports, cordless telephones, faxes, LAN access, and file transfers. Zeevo also offers the BlueOS proprietary operating system and supports Nucleus Plus.

The software flexibility permits the development of a host-supported application where much of the software is on a host PC. Or, it supports an enabler solution where only part of the software is on the device (a cell phone, for instance) and most of the software resides in the Bluetooth circuits. And, users can create fully embedded solutions, such as gaming devices, digital cameras, barcode scanners, headsets, keyboards, or a mouse, where all software resides in the Bluetooth chip (Fig. 3).

The quickest way to develop these applications is by using the TC2000 development kit. It includes two development boards, each with the TC2000, 4 Mbytes of SRAM, 8 Mbytes of flash, 2 UART ports, one USB port, eight general-purpose I/O lines, and JTAG capability. With this kit, all software, cables, and documentation are supplied.

Price & Availability
The Sierra Development Kit is currently available for $8000. Samples of the TC2000P-4 and TC2000M-E chips also are available now, and full production will start by mid-year. In OEM quantities of 1 million units, the TC2000P-4 costs $17.

Zeevo Inc., 2500 Condensa St., Santa Clara, CA 95051; (408) 982-8000; fax (408) 982-8008; www.zeevo.com.

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