DALLAS -- Texas Instruments Inc. here today introduced a new family of logic devices that TI said will enable designers of network systems to increase backplane data throughput as much as 300% without necessitating large-scale system redesigns.
The new Gunning Transceiver Logic-Plus (GTLP) family of devices is designed for parallel backplanes and allows live insertion without "glitching" data. They also are low-voltage devices, operating at 3.3 volts, that are 5-V tolerant.
"We found that designers are moving to 3.3 V, but there are still existing devices and circuits that they want to keep on the board that operate at 5 V, so we felt the 5-V tolerance was important," said Steve Blozis, product marketing specialist for advanced datacom solutions at TI. "They are looking for a higher frequency of operation on the backplane because that would translate to higher data throughput, which is the key with the Internet and all the applications out there now--everybody's looking for higher bandwidth."
Gunning transceiver logic is a reduced-voltage-swing logic (typically less than 1 V). The GTL Plus is a family specifically designed for backplane operations that combines the best of high- and low drive families such as ABT, LVT, and Futurebus+, said Blozis. These devices are designed for multi-slot medium- and heavily loaded backplanes, and are backward compatible with current logic.
The devices feature tight tolerance receiver threshold levels and significantly improved output edge control circuitry on the rising and falling edge of the GTLP outputs. These features help reduce line reflections and electromagnetic interference, and improve overall signal integrity, allowing clock frequencies of more than 80 MHz.
A key advantage is their ability to allow live insertion of cards rather than the hot insertion currently in use, where the data must either be turned off or re-sent. This capability is becoming critical in high-availability communications and networking applications, said Blozis.
"With our GTLP device operating at 100 MHz, a 32-bit parallel backplane can transfer data at 3.2 gigabits per second," Blozis said. TI sees applications for the chips in Internet routers, wireless base stations, ATM switches, Sonet/SDH multiplexers, mass storage, remote access and other types of systems where demand for increased bandwidth is rising.
"Everything's going to be hooked up to the Internet," Blozis said. "You want to watch T, it's going to be through the Internet, listening to stations coming through your alarm clock. That's all bandwidth."
The devices' CMOS manufacturing process reduces the static power consumption, "which is important in the flow-through pinout, making it easier for the designers to lay out," Blozis explained.
A bus hold option is available, said Blozis. Bus hold prevents logic devices from floating in the midrange--rather, they need to be either low or high. Resistors can perform this function, but "the bus hold option is a built-in feedback cell that keeps the logic device in the last known state. It's a good option to have, and reduces the part count on the board."
TI will offer the GTLP devices in a wide range of package options, including a small outline integrated circuit (SOIC), small-scale outline package (SSOP), think small shrink outline package (TSSOP), thin very small outline package (TVSOP) and a low-profile fine-pitch ball grid array (LFBGA). This allows designers to increase the performance and functionality of a system without increasing the size of the daughter card, Blozis said.
TI believes the GTLP family will allow systems to be designed faster as Internet traffic rapidly increases throughout requirements. "A lot of people use standard pinouts but they only support a certain frequency," Blozis said. "You'd have to do a large redesign of the equipment to get the higher data throughput." The GTLP family devices allow use of the existing boards and passive backplanes, with minor changes the termination scheme. And because the GTLP family is backward compatible with existing devices, "this will allow them to get the throughput with a smaller change required to the board."
Several GTLP devices are sampling now, with additional devices to be added during the next few months. Prices, in 1,000s, range from a low of $4.70 for the 24-pin, 8-bit SN74GTLPH306 bus transceiver (available in February) to high of $17.50 for the 114-pin, 36-bit SN74GTLPH32912 universal bus transceiver (available in June).