Tapped into the Future

-- Richard Mandel

The manufacture of products to serve the telecommunications market produces an army of new items on a daily basis. Yet demand still calls for increased functions in smaller packages, which in turn drives component and software companies to keep their engineering staffs at their design stations.

Caught in our editorial butterfly net were these three items and their applications, which typify the direction in which the telecommunications industry is flying:

Transforming the transformers

Pulse in San Diego, CA has been involved in transformers and magnetic devices for nearly 40 years, produces components used in LANs, analog and digital telecommunications and power supplies. The company began 1999 with the introduction of a low-profile, 16-pin, surface mount T1/E1 family of transformers that operate in environments with temperatures ranging from -40 to 85°C. Several months earlier, they introduced a similar product that contained eight transformers for quad-port applications in a 40-pin package.

The key function of Pulse's T1/E1 transformers is to provide electrical isolation and match impedance between the TNV (which stands for telecom network voltage) network and telecom equipment without distorting the data signal. In this sense, the transformers play a significant role in protecting the circuit to impede hazardous voltages which may cause damage to telecom equipments. At the same time, the transformers facilitate the transmission of data signal.

Both packages stand less than 0.25 in. off the surface of the PC board. A patented process, which Pulse calls their InterLock Base, creates a uniform positioning of the coils and interconnections between wires and lead frames. This reduces stresses associated with the handling of coils during the assembly process and transfer molding encapsulation. The package contains both transmit and receive transformers, with up to 4 transmit and 4 receive channels supported by the quad port units.

Typically, these transformers are used in such applications as WAN networking devices, Internet service provider (ISP) servers, multiplexers, digital access and cross connect systems (DACS), channel banks and cellular base stations.

Protecting the circuits

With over seven decades of manufacturing fuses and circuit breakers for applications from computers and cars to office towers, toys and ten ton trucks, Littlefuse, Des Plaines, IL, now offers surface-mount fuses made specifically for telecom OEMs. Engineers at Littlefuse point out the need for circuit protection -- always required in telecommunications applications -- to protect both product and end user. Today, circuits must pass requirements such as UL 1459/1950 3rd edition power cross, and comply with Bellcore GR-1089-CORE and FCC 47 Part 68 surge specifications. An overcurrent protector is usually paired with an overvoltage device and helps protect it from high current. The overvoltage component is used to limit peak voltage -- if this device fails in the shorted state, the overcurrent protector is required to open the circuit to prevent risk of fire or harm befalling the end user.

Development of new high-volume, reduced-size products has driven the need for devices suited to reduced PC board real estate. With a clearance height of 0.095 in. and outer dimensions of 0.200 x 0.590 in., the SMTelecom Fuse (436 Series) suits slim profile products such as PC-card or desktop modems, telephones and answering machines. The series has an operating voltage of 250V, and offers amperage ratings of 0.75A, 1.0A, 1.25A, 1.5A and 1.6A.

For the fuse body, Littlefuse used a melamine substrate, which closely resembles the typical PC board stock, FR4. This is important for considerations of TCE (thermal coefficient of expansion) and reliability. The compatibility between the materials will help decrease the likelihood of solder joint problems over time.

Strike up the bands

As cellular phones have grown to become as ubiquitous as liposuction in Hollywood, additional frequencies were added to handle the immense amount of service, plus all the carrier companies and systems. This brought about the evolution of cell phones that could handle more than one frequency, but necessitated additional receive/transmit circuitry to support each band. Having a single phone capable of more than one frequency also allows the unit to operate in virtually all of the world's major cities.

CommQuest Technologies, an Encinitas, CA, company that merged with IBM last year, recently introduced a single chipset package for all three GSM frequencies (900, 1800 and 1900 MHz). The Tri-Band GSM chipset consists of two highly integrated circuits, performing the functions from the audio/data/IO to the radio (RF) front-end interface. These circuits include a single CASP (Communication Applications Specific Processor) device for baseband and IF processing, in a 196-pin BGA package, and a tri-band RF transceiver in a 48-pin TQFP. Both devices operate at a minimum of 2.7V. Software bundled in the chipset enables roaming between all GSM frequencies, when permitted by network operators.

CommQuest states that use of the Tri-Band chipset will allow component count in a handset to be reduced from approximately 400 to 250. A proprietary 1-bit sampling technology also minimizes power consumption, with a current drain less than 90 mA in active mode. This could translate to five hours of talk time with a 3.6V, 1200 mAH battery. The Tri-Band package would provide multi-band capability for any wireless device and help usher in the next generation of "information appliances."

For more information, contact:

Pulse Engineering, Inc., 12220 World Trade Drive, San Diego, CA 92128. 619-674-8100. Circle 461.

Littlefuse, Inc., 800 E. Northwest Highway, Des Plaines, IL 60016. 847-824-0400. Circle 462.

CommQuest, 527 Encinitas Blvd, Encinitas, CA 92024-3740. 760-633-1618. Circle 463.