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Digital Recruits Enlist To Replace Veteran Analog Technologies

Dec. 13, 2010
Silicon Labs' Mark Downing considers silicon isolators in the context of silicon TV tuners and MEMs.

Remember tube amplifiers, rotary phones, and floppy disks? In their heyday, they were excellent technologies. But nowadays no developer would consider using them in a home theater system, telephone, or PC.

Why use yesterday’s technologies to design tomorrow’s products? Good question. Yet numerous antiquated technologies persist in the market because developers view them as economical safe bets.

Let’s consider optocouplers, can TV tuners, and crystal oscillators. While these tried-and-true technologies have been around for decades and continue to be used in current products, superior silicon-based alternatives are now available.

This year, we will see market shifts to 21st century innovations in each case: CMOS-based digital isolation products superseding optocouplers, silicon TV tuners leap-frogging can tuners, and microelectromechanical systems (MEMS) devices offering an alternative to crystal oscillators.

The End For Optocouplers
Opto-isolators or “optocouplers” have provided a preferred electrical isolation solution for more than 30 years. Prior to the 21st century, the technology to build optocoupler alternatives in cost-effective CMOS did not exist. This lack of options enabled optocouplers to dominate a decades-long captive market, despite their inherent drawbacks.

The operating parameters of optocouplers wander with temperature changes and device age. They are subject to light-output failure when operated at elevated temperatures. And they have voracious power appetites, scaling up to hundreds of milliwatts per channel.

The first digital isolation products appeared in 2000, finally extending the benefits of advanced CMOS technology (lower cost, lower power, and higher performance) to isolation applications. CMOS isolators exhibit none of the issues plaguing optocouplers described above.

These devices offer stable operating parameters over temperature and voltage, fast timing performance, and exceptional transient immunity. They also provide high integration (up to six channels per package), low-power operation (down to 7 mW per channel), and much higher reliability than optocouplers.

Given the advantages of CMOS isolators over optocouplers, the market has been surprisingly slow to adopt them. But the age of the optocoupler is coming to an end. Digital isolator suppliers are making headway into the sweet spot of the $1 billion optocoupler market, with digital isolator sales now approaching $100 million annually.

Even established optocoupler suppliers are future-proofing their portfolios with digital isolation products. Although optocouplers won’t disappear overnight, we’ll see signs of rapid market acceptance of digital isolation technology in 2011 and beyond.

TVs Finally Kick The Can
Can tuners, rotating channel dials, and cathode ray tubes (CRTs) have been TV set fixtures for decades. Dials and CRTs are history, but the venerable can tuner lives on in digital TVs. Yet according to iSuppli, its days are numbered as TV makers migrate to silicon tuners this year, with more than 60% of TV sets expected to adopt this technology by 2014.

A can tuner consists of a mixer oscillator phase-locked loop (MOPLL) IC and an analog TV demodulator surrounded by up to 200 discrete components housed in a metal can. In recent years, TV makers have started to replace can tuners with silicon tuners to reduce cost and complexity, harmonize across regional standards, and shrink form factors.

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Advanced silicon tuners, which integrate the MOPLL, demodulator ICs, and most of the discrete components into a single-chip IC, now match and in some cases exceed the performance of can solutions, enabling TV makers to deliver improved picture quality and better reception for analog and digital broadcasts.

As TVs grow slimmer and adopt dual-tuner designs and multimedia reception while requiring bill of materials (BOM) cost reductions, can tuners cannot fit the TV industry’s form factor and price point needs. Can tuners also require considerable design and manufacturing resources as each can must be tuned manually—an unwelcome prospect with rising labor costs.

Today’s silicon tuners enable a more economical, streamlined manufacturing process, support dual-tuner designs, and allow TV makers to reduce the size and cost of their front-end solutions. Silicon tuners also can be implemented directly on the TV motherboard or inside a can module.

Some TV makers may choose a two-step approach, first using a silicon tuner inside a module and later directly on-board for the ultimate cost savings. Although can tuners will be around for a few more years in legacy designs, silicon tuner adoption rates are expected to rise exponentially in 2011 TV models.

MEMS Resonates In Timing
Quartz crystal oscillators provide the heartbeat for countless electronic applications, from clocks and watches to radios and cell phones to computers and telecom equipment. Crystal oscillators have been around since the 1920s, and their usage in electronics surged with the explosive growth of the semiconductor industry.

Billions of quartz resonators now ship annually, amounting to a roughly $2 billion market. Offering unparalleled temperature stability, the quartz resonator remains one of the electronic industry’s last critical components to be supplanted by silicon integration.

Since the early 1980s, microelectronics engineers have tried to develop commercially viable replacements for quartz resonators based on MEMS technology, which has been applied to sensors with great success. But creating MEMS resonators that match the temperature stability and performance of quartz has been problematic, not to mention the significant manufacturing challenges.

Several timing chip innovators have made progress on the MEMS resonator front this decade, addressing a range of technical challenges including temperature stability, power reduction, packaging, and single-chip CMOS integration.

The nascent MEMS resonator market began showing a strong pulse the past couple of years, with competition heating up and one breakthrough after another being heralded. As a result, 2011 will be a tipping-point year for MEMS resonator commercialization. Novel solutions will address many of the difficult technical problems.

For the first time in the long history of the timing industry, emerging MEMS resonator products will begin to displace quartz, providing the benefits of silicon integration: smaller footprint, lower cost, higher reliability, and the potential to integrate the resonator function in single-chip solutions.

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