Multi-Channel CDR handles high-speed SONET applications.

Press Release Summary:

Supporting OC-3/OC-12 data transmissions speeds, Model XRT91L34 quad-channel clock and data recovery (CDR) circuit accepts high speed NRZ serial data from LVDS or LVPECL receiver and generates clock signal with same frequency as incoming data. Unit integrates Phase Lock Loop (PLL) technology, and features 4 channels that share single 77.76 or 19.44 MHz reference clock. Available in 128-pin LQFP package, it operates at 1.8 V core with 3.3 V tolerant I/Os over industrial temperature range.

Original Press Release:

Multi-Channel Device Can Lower Bill-of-Material (BOM) Costs, Reduce Board Space Requirements and Simplify Design

Fremont, California, October 29, 2007 - Exar Corporation (Nasdaq: EXAR) announced the release of an industry-first, highly-integrated multi-rate quad-channel CDR that supports OC-3/OC-12 data transmissions speeds, the XRT91L34. This device accepts high speed NonReturn-to-Zero (NRZ) serial data from the Low Voltage Data Signal (LVDS) or Differential Low Voltage Positive Emitter Couple Logic (LVPECL) receiver and generates a clock signal the same frequency as the incoming data. This functionality supports high-speed SONET applications such as SONET repeaters and extenders where data signals travel across system boards or backplane connectors requiring advanced CDR capabilities.

"The XRT91L34 integrates Exar's superior Phase Lock Loop (PLL) technology, provides a multi-data rate CDR and helps improve system performance due to enhanced features that improve jitter characteristics," said Rakesh Bhatia, product line manager, Optical Networking and Storage. "As the market continues its movement to smaller and more highly integrated systems, the XRT91L34 provides a key advantage for network infrastructure solutions."

Product Features

All four channels of the XRT91L34 share a single 77.76MHz or 19.44MHz reference clock. System architects implementing the XRT91L34 ensure increased design flexibility when choosing an external reference clock because the XRT91L34's PLL can lock to either the reference clock or incoming serial data stream. If the recovered clock frequency deviates from the local reference clock by more than ±500 ppm, the clock recovery PLL locks back to the local reference clock. When this occurs, a Loss of Lock (LOL) or Loss of Signal (LOS) is declared and the CDR will continue to supply a recovered clock (based on the local reference) to the framer/ mapper device.

The XRT91L34 comes with additional features such as Signal Detect (SDEXT) that helps ensure data accuracy. When the SDEXT is de-asserted by the optical module, or when internal Loss of Signal Detect (DLOS) is asserted, the receive serial data output will be forced to a logic zero state for the entire duration that a LOS condition is declared. This acts as a receive data mute upon LOS function to prevent random noise from being misinterpreted which ensures higher accuracy of transmitted data. When the SDEXT becomes active, and the recovered clock is determined to be within ±500 ppm accuracy, the device continues to recover the clock and data in a normal mode.

Prices, Packages, Availability and Additional Information
Samples of the XRT91L34 are available now. The device is in a 128-pin LQFP package and operates at 1.8V core with 3.3V tolerant I/Os over the industrial temperature range. In 1k quantities the XRT91L34 is $21.40 and additional information on this product can be found at Additional information on other SONET/SDH products can be found at

About Exar
Exar Corporation is Powering Connectivity by delivering highly differentiated silicon solutions empowering products to connect. With distinctive knowledge in analog and digital technologies, Exar enables a wide array of applications such as portable devices, home media gateways, communications systems, and industrial automation equipment. Exar has locations worldwide providing real-time system-level support to drive rapid product innovation. For more information about Exar visit:

Greg Kaufman, Marketing Communications
(510) 668-7000


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