Electronic Design

Mini GSM/GPRS Radio Shrinks Cell-Phone BOM

Projections for the cell-phone industry show 700 million units in 2005. Many of these new phones are replacements and upgrades. But there's also the onslaught of feature phones with cameras, color screens, MP3 or AAC compressed audio, video, and even hard drives.

These phones have created a bevy of cost and space demands. In response, Analog Devices' Othello-G module measures 1.8 by 0.85 mm, or 1 cm2 (see the figure). It cuts component count by 75% as well.

Also known as the AD6548, the Othello-G targets dual-, tri-, and quad-band GSM/GPRS phones. It's compatible with GPRS Class 12 packet operation, featuring a duty cycle up to 50%. The radio's complete direct-conversion design integrates four fully gain-programmable low-noise amplifiers with a 77-dB gain control range.

Receiver sensitivity ranges from ­109 to ­110 dBm for a 2.4% bit error rate. The device also contains a fractional-N frequency synthesizer phase-locked loop, a single voltage-controlled oscillator, and loop filters on-chip. A 26-MHz crystal is used as the reference. A three-wire serial interface programs the IC.

Three on-chip low-dropout regulators save space and let the device operate directly from a battery in the 2.9- to 5.5-V range. In power-down mode, current drain is 10 µA maximum. The receive surface-acoustic-wave filters are external, as are the dual power amplifiers, the transmit/receive switch, and a few decoupling capacitors. The interface to the baseband chip is via the usual analog I/Q signals.

The chip can be paired with Analog Devices' SoftFone Blackfin baseband chips. These DSPs are entirely RAM-based, so it's easier and quicker to make changes, add features, or upgrade the phone.

The AD6448 comes in a 32-pin LFCSP-32 package. It's available now for $3 each in quantities of 10,000 units.

Analog Devices Inc.
www.analog.com
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