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Subscriber Line Interface Integrated Circuit Suits Wireless Local Loop Networks |
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 Designers of equipment for short loop telephone systems will welcome STMicroelectronics' new STLC3055 Subscriber Line Interface Circuit, the only single chip SLIC on the market that operates on a single positive supply voltage of 5.5V to 15.8V All of the voltages needed for SLIC operation are generated internally in the STLC3055 by a dc-dc converter block integrated on the chip. Moreover, power dissipation in the chip is minimized by the high efficiency of this converter and also by reducing the line voltage from -70V to -52V in the off hook state. Fully functional even at 5.5V, the STLC3055 extends the effective life of emergency backup batteries because it continues to function even when the battery voltage is very low. This feature makes the chip ideal for Wireless Local Loop equipment which is widely distributed and cannot be remotely powered from a central office battery. Other features useful in WLL applications include integrated ringing and a high level of integration that reduces printed circuit board area. The same features make the device suitable for ISDN Terminal Adapters. The STLC3055 includes all of the key features needed to implement Wireless Local Loop and ISDN-TA SLIC solutions, offering integrated ringing, on-hook transmission, a high impedance mode, hardware-set off-hook thresholds & limiting current, metering pulse injection, polarity reversal and integrated thermal protection. Assembled in a compact 10mm x 10mm 44 lead Thin Quad Flat Pack, it operates over an extended -40 to +85oC temperature range to enhance reliability. Battery feed functions are supported by the on-chip dc-dc converter which is a single-ended buck-boost architecture capable of supporting line voltages from -7V to -70V, changing dynamically depending on the operating mode and the line length or load. Special care has been taken in the design of this block to avoid faulty operation in the presence of unpredictable overload conditions. The converter uses a PWM approach at a synchronous frequency selectable in the 90 to 125kHz range; this choice simplifies EMI filtering and noise control. Additional flexibility is provided by an externally hardware programmable maximum input peak current to support a large variety of battery and system solutions The Sti5500, the first member of the OMEGA family, was one of two products developed by STMicroelectronics that were awarded the prestigious European IT Prizes by the European Commission in conjunction with Euro-CASE, the European Council of Applied Science and Engineering, in November 1998. From a field of nearly 300 nominations, 25 winners were selected by a panel of independent experts from 16 European countries. ST was the only semiconductor manufacturer among the prize winners and was the only company to win two separate nominations for the Grand Prize. In a Wireless Local Loop network, the final connection to the telephone is a short range radio link in place of the traditional copper wire. This approach is cost effective in densely populated urban areas because the cost of providing wireless coverage is less than that of installing cables. Another important advantage for new service providers is that investments generate revenue almost immediately. To connect a new subscriber, the service provider installs a standard wired phone connected to a radio link attached to the wall of the building. STMicroelectronics provides all of the key integrated circuits for this wall box, including the STLC3055 SLIC, the ST5088 Codec and cellular phone circuits. STMicrolectronics is a major supplier of dedicated integrated circuits for telecom applications, offering a product range that includes ICs for ADSL, modems, cellular phones, cordless phones, pagers, wired terminals, internet phones, line cards, ISDN, Wireless Local Loop and other applications. |
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