Settable equalizer increases copper throughput to 6.25 Gbits/s

Santa Clara, CA – Quellan Inc. builds upon its industry leading Signal Integrity product line, a complex analog integrated circuit portfolio, with the introduction of its EQ601 CMOS settable equalizer. Quellan's EQ601 Equalizer Technology enables low cost copper system interconnections up to 6.25Gbps and effectively extends the useable length of copper cable in point to point communications applications.

Quellan's EQ601 is primarily used for card to card and shelf to shelf interconnections between the nodes in communication systems. By performing active signal conditioning of attenuated NRZ data due to high frequency transmission medium losses, Quellan's EQ601 extends signal reach and increases channel throughput.

The EQ601 provides unique features for next generation systems by using a combination of dynamic tuning and performance monitoring that allows engineers to address the widest range of trace boost settings and to easily determine the quality of the resultant eye pattern ” without expensive test equipment. If channel characteristics change over time, signal integrity can be optimized automatically with these features.

Unequalized signal after 30 inches on FR4

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Unequalized signal after 30 inches on FR4

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“The EQ601 allows vendors to future proof systems including wireless , storage and network infrastructure products with a tiny, low power single chip,” said Tony Stelliga, Quellan's President and CEO. “The settable nature of the EQ601 allows it to improve performance on legacy and future systems, while the performance monitor provides a dynamic indication of signal quality – under software control.”

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Quellan's EQ601 uses DC-coupled current-mode logic inputs/outputs and is available in a 4mm x 4mm 24-pin leadless LLP package. The EQ601 is fabricated in a 0.13 micro CMOS process and operates from a 1.2V supply over the -40 to +85 C temperature range and consumes only 90mW of power. Price is $7.65 (10,000—up, FOB USA).

Quellan, Inc. is a provider of analog signal integrity semiconductor solutions. Quellan serves the computing, communications, broadcast and radio frequency markets with its Collaborative Signal Processing Architecture. For more information, visit the Quellan website.

I appreciated the briefing from Tony Stelliga and the Quellan engineering staff. They took the time explain the advantages of a resettable equalizer, over a fixed or an adaptive type. Such briefings are always helpful to engineers who want to know how things work. They instill a lot of confidence: As a student (and after years of technology reporting, I'm always learning new things), they become the people from whom I can count on learning new things. If I were in a position to buy ICs, these are the people with whom I'd want to do business with.

As with all equalizers, signal fidelity and clarity can be increased by boosting certain frequencies on the transmission path, and attenuating others. The kind of boost or attenuation you apply always depends on the frequency of the signal you're transmitting, and what you think is likely to happen to it along its transmission path. Transmitting Gbits/s signals over copper — even short distances — is always a bear.

Here's what I learned about the Quellan EQ601, which is intended for card-to-card transmissions across a backplane (or, in some cases, card cage-to-card cage transmissions up to 5 meters): There are a lot of different transmission schemes operating the in range from 2.5 to 6.25 Gbits/s. These include Sonet OC-48 (which centers, not at 2.5 GHz, but 2.48832), Fibre Channel (which, like 10-Gits Ethernet, uses multiple screams of 2.5 GBits/s) and the newer AdvancedTCA telecommunications backplanes (transmitting from 3.125 to 6.250 Gbits/s). In addition to different corner frequencies, you have differing attenuation patterns in the signal imposed by differences in backplane materials and length. Quellan came up with a receive-side part that could service each of these applications.

A fixed-function equalizer offers the best balance between small size, high-performance and low cost with a dedicated analog component, Tony Stelliga explains. The problem is that a somewhat different part would be needed for each application in the 2.5-to-6.25-Gbits/s range.

Conversely, a self-adaptive IC raises the size and cost of the circuitry, and doesn't always function as it should. “It often goes on a hunt and gets lost,” Stelliga says. This error shows up after a long string of zeros on an NRZ data stream. The adaptive parts will often fail to latch the initial data one on the tail end of that stream, he explained.

The user-settable EQ601 equalizer has the “robustness” of a fixed equalizer, by carefully controlling received amplitudes, but also the flexibility required to accommodate variable trace lengths.

The DSP or not to DSP

An adaptive technology based on digital signal processing would be too costly in terms of size and power consumption for the legacy applications for 6.25 GBits/s and below, Stelliga explained. “These things need to look like surface mounted chip capacitors on the line card,” he said. (The EQ601 comes in a 4 x 4-mm package.) He didn't rule out the use of DSP for new-generation 10-Gbits/s applications, however.

Quellan's skill set includes modulators, equalizers and noise cancellation systems for high-speed communications systems. Based on In-Stat projections, Quellan sees a $900-million market opportunity for its equalizers and noise-cancellation chips — $160 million enterprise and telecom servers, $220 million in desktop computing and consumer electronics, $160 million in storage, $60 million in Broadcast, and $230 million in Wireless basestation applications. Target customers for Quellan parts include system builders like Cisco, Thomson, Sony, EMC, McData, Samsung, and Motorola, Quellan says.

More about the 601

The device is built in 0.13 micron CMOS (and upgrades the earlier EQ600, built in 0.18 micron CMOS). Quellan claims its CMOS device has superior jitter performance over longer trace lengths on FR4 circuit boards than equalizers and transceivers built in SiGe. Jitter is less than 45 ps for trace lengths up to 30 inches.

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The EQ601 allows for per channel tuning settable boost level. Users can choose from one of 32 discreet levels using a serial I2 C interface. The equalizer boost compensates for attenuated NRZ data at very high frequencies (6.25 Gbits/s, 2.5 Gbits/s, 3.125 Gbits/s, and 5 Gbits/s). An integrated performance monitor registers any degradations in signal integrity and allows re-tuning.

The equalizer circuit uses dc-coupled current mode logic (CML) inputs/outputs. It operates from a dual 1.2V and 2.5V supply, and consumes 90mW typically.

It is packaged in a 4mm x 4mm 24-lead MLF.

Click here for the datasheet.

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