Electronic Design

Single-Chip TV Tuner Exceeds Performance Expectations

Semiconductor companies have been working for years to develop a fully integrated TV tuner, and some progress has been made. Yet even the most recent designs have their disadvantages. Many only just meet the various test standards, while others require more than a few external components to do the job.

The Si2170 from Silicon Laboratories, though, is the first silicon TV tuner to exceed the performance of traditional discrete TV tuners. It improves picture quality and reception for both analog and digital broadcasts. This single CMOS IC hybrid (analog and digital) not only complies with all global standards, it also exceeds the performance of traditional can TV tuners. It’s designed for digital TV sets, set-top boxes, and PC TV applications.

The tuner fits both analog and digital designs while reducing external component count, complexity, and manufacturing costs. Also, it addresses the desire of TV set manufacturers to make sets ever slimmer. It supports U.S. ATSC and cable quadrature amplitude modulation (QAM) as well as European DVBT/ C and Japanese ISDB-T/C digital standards. It covers the legacy NTSC, PAL, and SECAM analog standards with its built-in analog demodulator as well.

The Si2170’s performance is far beyond even the best discrete component “can” or IC tuners. It optimizes both the sensitivity and blocking metrics of TV tuner standards where both of those factors are often traded off of one another. It does this with a unique merged low-noise amplifier (LNA) and a high-Q tracking filter up front to provide gain only around the desired channel frequency. This enables higher sensitivity in crowded spectrum conditions with strong undesired signals.

The highly linear front end with its IP3 greater than 20 dBm avoids overload and minimizes RF gain back-off. The input, which can be anything in the 42- to 1002-MHz range, goes to the LNA and tracking filter (Fig. 1). It’s then sent to the mixers where the low-IF (3- to 5-MHz range) or zero-IF architecture takes over to deliver the digital video output. A built-in analog demodulator recovers the composite video and audio.

The Si2170 is designed to work with the Silicon Laboratories Si2165 digital TV demodulator chip. The internal frequency synthesizer sets the channel. The tuner doesn’t need external surface acoustic wave (SAW) filters, which are generally required to provide the IF selectivity. All filtering is done on the tuner chip, greatly slashing the cost and space requirements in a TV set.

The Si2170 is made with plain-old low-cost CMOS instead of the biCMOS (some with silicongermanium) used by other IC tuners. It operates from 1.8- and 3.3-V power supplies and consumes about 1 W. It is housed in a 7- by 7-mm, 48-pin quad flat no-lead (QFN) package (Fig. 2). The reference design, which is 1.3 by 1.7 cm and 2.5 mm thick, includes the metal shield. I bet Silicon Labs will soon have another version incorporating its Si2165 digital demodulator as well.

LOUIS E. FRENZEL

SILICON LABORATORIES INC.
www.silabs.com

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