Electronic Design

Single-Chip Tuner Puts FM Broadcast Radio Just About Anywhere

Despite its age, low-tech image, and mounting competition with satellite systems, FM radio still has an enormous following. It remains a major purveyor of music for car and home stereos. With Silicon Laboratories' one-IC radio tuners, engineers can now put FM radio in an array of applications, like cell phones, PDAs, MP3/AAC players, portable radios, notebook PCs, and car radios.

The Si4700 and Si4701 are complete one-chip FM radios implemented fully in CMOS. They work with external audio power amplifiers (PAs) and a controller for tuning. The controller also helps implement Europe's Radio Data System (RDS) and the U.S. Radio Broadcast Data System (RBDS), which enable the display of station call letters, frequency, song titles, artists' names, and other short messages. The Si4701 chip supports RDS and RBDS.

The only external components needed are a 32.768-kHz clock and a 2.7- to 5.5-V dc supply and bypass capacitor. An on-chip regulator supplies all circuits. The radio uses the common I and Q datapaths with mixers, a low 128-kHz IF with internal filter, an analog-to-digital converter, DSP filtering and demodulation, and digital-to-analog converters that drive the external PAs. The headphone cable serves as the antenna. The radio integrates all of the usual features, like automatic gain control, automatic frequency control, seek tuning, mono or stereo, programmable de-emphasis, volume control, bass boost, and adaptive noise cancellation.

The Si4700 and Si4701 both come in a 4- by 4-mm QFN package. In 10,000-unit lots, the Si4700 and Si4701 cost $3.00 and $3.45, respectively. Full production quantities are expected in the fourth quarter of 2005. Also, an evaluation board is available for $150.

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Silicon Laboratories
www.silabs.com

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