Texas Instruments Inc. (NYSE: TXN) isn't normally associated with the high-speed Sonet/SDH transceiver market. But it's determined that its first stab at an OC48 chip will put it in the limelight.

TI has unveiled a chip that integrates a multirate Sonet transceiver with several other circuits. And it claims the product consumes roughly half the power of other Sonet chips. In short, TI's claiming a breakthrough that could let manufacturers create better DWDMs (dense wavelength-division multiplexers), Sonet gear, and digital crossconnects.

But experts say there might be some key pieces missing from TI's offering -- such as Sonet framers and lasers.

Dubbed the SLK2501, TI's new product is a CMOS (complementary metal-oxide semiconductor) chip that supports bidirectional OC48 (2.488 Gbit/s), OC24 (1.244 Gbit/s), OC12 (622 Mbit/s), and OC3 (155 Mbit/s) data rates. It comes with an integrated multiplexer-demultiplexer, a clock/data recovery (CDR) unit, and a clock generator. TI says the chip also contains a pseudo-random bit-stream generator, giving a built-in bit error rate testing function.

The real benefit is that the SKL2501 consumes considerably less power than other Sonet chips, which don't feature the same level of integration, says TI. "The SLK2501 consumes 650 to 700 milliwatts of power. Comparable Sonet chipsets with OC48, CDR, and mux/demux capabilities consume about 1.2 watts," says marketing manager Atul Patel.

What TI doesn't provide are the Sonet framers required to ensure that data going into and out of the chip will be properly formatted for use on an optical network. Without that piece, some sources say, the chip is lacking. "This chips sounds interesting. But you need to be able to have framers for all speeds supported in the chip. Unless it has that, it's not much use," says Nan Chen, director of product marketing at Force 10 Networks Inc., a ten-gigabit Ethernet startup.

TI disagrees. The chip, spokespeople say, is designed to link to framers and ASICs (application-specific integrated circuits) developed for each customer by TI's custom development group. Having a low-power, multirate building block streamlines the process.

TI also doesn't make the lasers required to work with this chip in real optical products. It says these are in development. In the meantime, however, customers will have to go elsewhere to get these vital components. They may not be very happy about that because it's easier to get components from one supplier -- since that facilitates product compatibility and enables discounts.

Despite these drawbacks, TI seems to have achieved a breakthrough on at least one score. Rival Sonet chipmakers Applied Micro Circuits Corp. (AMCC) (Nasdaq: AMCC), PMC-Sierra Inc. (Nasdaq: PMCS), and Vitesse Semiconductor Corp. (Nasdaq: VTSS) don't yet offer multirate Sonet/SDH chips with integral CDR capabilities.

And these companies acknowledge the need for single-chip solutions. "We have chips that fit this description without CDR," says Mike Furlong, product marketing manager at Vitesse. "We are coming out sometime within the next few months with an integrated chip. The ideal is a small module -- one chip integrated with these functions and a PHY [physical layer interface] behind."

TI says its transceiver chip is sampling now and will ship in volume in April 2001.

-- Mary Jander, senior editor, Light Reading http://www.lightreading.com