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Toshiba Expands OC-192 Receiver Product Line - Adds PIN Receiver Modules With Integrated Transimpedance And Limiting Amplifiers

New 10Gbps receivers offer higher integration in smaller packaging for more efficient design

The manufacturer says . . .

ChipCenter's Paul O'Shea says . . .

Reinforcing its commitment to the optical communication market, Toshiba America Electronic Components, Inc. (TAEC) announced two new 10 gigabit per second (Gbps) PIN receiver modules featuring an integrated transimpedance amplifier (TIA) and limiting amplifier, targeted for full-featured intermediate reach SONET telecommunications and data communications applications. The integration of the limiting amplifier with the TIA facilitates compatibility between these two stages while simultaneously reducing the number of high speed interconnects required for end-designs. The new devices were developed by Toshiba Corp. (Toshiba) to meet the demands for increased functionality in a compact design, while providing design engineers with the option to adjust the decision threshold point in order to optimize bit error rate (BER) performance. ıToshiba is no stranger to the trend toward increasing functionality and capacity per square inch,ı said Jay Heinecke, director of business development, TAECıs optoelectronic products. ıWith our latest OC-192 integration, weıve done just that, giving design engineers the performance they demand while enabling them to more easily create effective solutions for todayıs space-conscious applications.ı Designated TOPD373-RXA and TOPD373-RXB, the new Toshiba receivers offer the same performance as the companyıs previous generation 10Gbps PIN receivers while requiring less board space. The TOPD373-RXA is housed in a Multi-Source Agreement (MSA) package measuring 12.7mm x 20.8mm x 6.9mm. The TOPD373-RXB is housed in a smaller, flangeless package measuring 16mm x 12.7mm x 5mm. Diversifying its extensive receiver line up, which includes 2.5Gbps up to 10Gbps devices, these new Toshiba devices provide added integration of the limiting and TIA amplifiers. Toshiba also offers a line of 10Gbps transponders with transmit and receive functions within an integrated module, providing added flexibility to the designer and shortening design cycle time. ıAs a result of increasing demand from end-users, next-generation SONET services are beginning to expand beyond the core networks into the intermediate-reach networks,ı said Jason Marcheck, senior market analyst, Pioneer Consulting, a Boston-based research firm. ıThe development of more highly-integrated and compact optical communications devices will enable network operators to more efficiently manage the growing need for increased bandwidth, while optimizing the performance of enhanced services including data, voice and video.ı TAECıs website: http://www.chips.toshiba.com/

The TOPD373 RXB and RXA, are similar products available in different packages. The RXA device is an MSA-compliant package and meets the groupıs footprint requirements; the RXB is a coplanar or flangeless package. Toshiba is adding these devices to their existing line that they have supported for 17 years. With this product the company says they are trying to broaden their market offering as well as their customer base. Both these devices are PIN-based devices (a pn junction with a doping profile tailored in such a way that an intrinsic layer - the I-region - is sandwiched between the p-layer and the n-layer, thus P-I-N) and contain a PIN photodiode going into a preamplifier or transimpedance amplifier, and then going into a limiting amp as well. The function of the limiting amp is to convert the photodiode current into a voltage, which then goes into the limiting amp. The limiting amp behaves as a linear amp up to a point at which time it flattens out in response and gives a fixed output, even though the input might increase, so that engineers when they are applying these devices know what to expect on the output range. Both devices have differential outputs for noise immunity. Whatıs interesting about the RXA series is that it has a decision threshold control pin. That allows you, in certain applications such as a receiver card for example, to optimize the voltage to determine where the ones and zeros are in a bit stream. You can optimize the bit-error rate performance in a noisy environment and get the best performance out of a receiver card. The RXB series does not offer the capability to adjust the decision threshold. What it offers instead is a more common feature, a loss of signal alarm. It also offers a pin that allows you to monitor the optical input to the amplifier circuits inside the device, and you can monitor the output of the photo diodes from one of the pins on the device. Another feature it provides is a built-in threshold voltage that it generates off the Vcc so you can set your loss of signal alarm by using the internal voltage. The ability to adjust the threshold is a pretty nice feature because it allows you to adapt to the noise caused by different customer cabinets or by different operating environments. It allows you to determine what constitutes a noise problem once itıs out in the field. You can actually simulate the noise in the lab and minimize the impact on error rate by using that threshold adjust feature. The integration of the limiting amp and the TIA, facilitating compatibility between the two stages, makes it easier for the guys designing the cards because they donıt have to add that amplifier as part of their circuitry, itıs built into the module. So all you need to know about is the voltage range you have to deal with over a certain range of optical inputs. Earlier receivers on the market are basically just a photodiode with a very high quality TIA. They donıt provide the limiting amp that is basically considered a 1R receiver, or a photodiode with a TIA. These products from Toshiba are 2R. The addition of the limiting amp makes it a 2R device (the Receive and Regeneration functions). Regeneration is the voltage range you expect to see over a given optical input. In the optical space 3R indicates a receiver has a CDR function (clock and data recover) so it can regenerate the timing that the original data had. Samples of the TOPD373-RXA and TOPD373-RXB are scheduled to be available now, priced at $1,600 each. Mass production is slated for late third quarter 2002. TAECıs website: http://www.chips.toshiba.com/. E-mail: tech.questions@taec.toshiba.com. Data sheet: The data sheet was not posted at the time of this review but when it is available you can find it at Toshiba's website.

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