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Silicon Laboratories Extends Industry-Leading DAA Technology To Voice Telephony Applications

Si3050 Delivers Global Compliance in Smallest and Lowest Cost Solution

The manufacturer says . . .

ChipCenter's Paul O'Shea says . . .

Silicon Laboratories Inc. announced the Si3050 global silicon direct access arrangement (DAA), which expands the company's industry leading product family into voice telephony applications that require higher performance and enhanced features. Like existing members of the DAA family, the Si3050 is programmable to meet global telephone line standards allowing one solution to be implemented worldwide. By reducing the number of external components needed for a full feature telephone interface, the highly-integrated Si3050 saves up to 30 percent in cost and 75 percent in board space compared to existing transformer-based solutions. These benefits are ideal for multi-channel voice products, including private branch exchanges (PBXs), voice enabled routers, computer telephony systems, pairgain systems and Voice over Internet Protocol (VoIP) applications. At less than two square inches per port, the Si3050 allows telecom equipment manufacturers to implement more voice channels per card than any other competing solution. The globally-programmable Si3050 reduces manufacturing and inventory costs by eliminating country-specific product versions. Additionally, the DAA architecture is designed to minimize software development while maximizing flexibility and performance. "In today's market environment, telecom equipment manufacturers are concerned with greater port density and global compliance," said Jeremey Donovan, vice president and chief analyst for Gartner Dataquest. "Solutions that enable manufacturers to achieve these attributes at an affordable price are highly sought after in today's cost competitive environment." "Our DAA technology has achieved great success in the computer soft modem space," said Dave Bresemann, vice president of Silicon Labs. "The Si3050 expands the opportunity of our DAA product line by addressing voice telephony applications, which present a significant new opportunity for our proven technology." Supporting both PCM/SPI and GCI interfaces, the Si3050 is compatible with Silicon Labs' Si3220/Si3225 Dual ProSLIC(tm), which provides two-channel analog telephony interfaces for the sourcing side of telephone networks. With the addition of the Si3050, Silicon Labs provides the complete mixed-signal solution for both traditional access networks and customer premise telephony applications. Based on Silicon Labs' patented ISOcap(tm) technology, the Si3050 is a two-chip solution consisting of a line-side and system-side device, which are separated by two low-cost, high voltage capacitors eliminating the need for bulky transformers. The Si3050 includes a host of new features that provide unparalleled functionality, including 16 software selectable AC terminations, an 8- or 16-bit voice interface, a programmable hybrid to allow adjustment to real world line conditions and the ability to gain or attenuate telephone line signals in increments of 0.1dB. Using a single bill of materials and printed circuit board (PCB) design, the Si3050 is fully programmable to meet global telephone line standards including FCC, TBR-21, NET4, JATE and country-specific PTT requirements. Silicon Labs website: www.silabs.com

Big things are happening in small packages and that is certainly true for this product. This is not a me-too product but one that extends the use of a capacitive technology in a way no one had thought to use it. Designers will want this product because it shrinks the board space required, lessens the weight, and reduces the bill of materials. This is not a bad trio of reasons for selecting a design. The standard function of the Direct Access Arrangement (DAA) begins at the Central Office (CO), which requires a certain line termination such as an AC or DC impedance termination. Additionally, at the CO you need a certain signal level for dial tone or pulse dialing as well as a signal level for transmitting information by voice. Typically, the DAA supplies the line termination as well as some safety functionality. For example, since the telephone line that runs outside your house is subject to all kinds of events including lightning surges it needs to be protected. The way thatęs done is to divide the customer premises into a high-voltage and low-voltage section. The usual method to isolate these sections was with a transformer. Silicon Labs figured out a way to isolate the high/low voltage sections capacitively. They call the design ISOcap technology. The Silicon Labs DAA design uses two chips. One chip from the local side has a digital interface to the DSP that goes through the ISOcap interface. The ISOcap provides the capacitive isolation that is also a digital communications link to an analog chip on the high-voltage side. With the digital communications across the capacitive link they can program the mixed signal chip on the high voltage side with many line terminations. They also have a CODEC on the high voltage side that allows the data to be digitized and sent across the capacitor digitally. The caps are lighter, cheaper and smaller, and have better densities than transformers. Additionally, the transformer to the phone line uses an analog design and that limits its flexibility. So if you wanted to make a design for the US and Europe you would have to use different boards because there are different requirements for the terminations. The Si3050 chipset includes the Si3050 and the Si3019. The 3050 is the digital chip that sits on the low voltage side and the 3019 is the mixed signal chip that sits on the high voltage side. These chips are made in the standard 0.25-micron CMOS process, not in high voltage CMOS. Although the mixed signal chip is sitting on the high voltage side it doesnęt see those voltages because it is isolated through the capacitive barrier. There also is an external set of components around that mixed signal chip to handle the higher signaling voltages of the telephone line. So what is the capacitive isolation technology? Simply put, it isolates the customer premise equipment from the phone line. Although the capacitive isolation technology isnęt new, what Silicon Labs offers that is different is a chip set with a split architecture. It uses the ISOcap capacitors to send digital data to communicate between two chips that are physically isolated. Then Silicon Labs does some unique things. First, the 3050 that sits on the system side, doesnęt need a power supply from the system because it has a 3.3V power supply. But the mixed signal chip, the 3019, that sits on the phone line interface, doesnęt have a power supply. Initially it is powered by sending power across the capacitor to the 3019 chip. Once the phone goes off hook it uses a little bit of the loop current supplied by the phone line to power the chip. Thatęs pretty unique to allow that chip to be on the telephone line but not require a power supply. The chips have a DSP on them that have application software written for the DAA. To meet the telephone line standards the company uses programmable registers that alter the line interface characteristics. SL looked at the telephone line standards from around the world to determine the design bounds for the line interface but also allowed them to be flexible so any changes in standards can be met by manipulating some registers via the customeręs software. The 3050 provides PCM, GCI, and STI interfaces. There also are 16 built-in AC terminations that allow you to make slight adjustments in case you need better matching. Older implementations used a discrete DAA with a transformer that was country specific. It required separate boards for different countries and used a single multi channel CODEC depending on how many channels you wanted to port. That solution was quite large and the BOM was large for the international companies needing to support different country requirements. For example, the board area needed for one channel would be about 4 square inches. The 3050/3019 only takes up about 1.5 square inches. Other companies offer a non-transformer type solution but they typically offer optical isolation. The optical couplers are more expensive with more components. These solutions donęt generallt save any board space compared to transformer solutions. Additionally, optical couplers typically have a large BOM depending on the requirements of the design. For example, for PBXs you have a couple variations to go off-hook, one is called ground start and the other is called loop start. For some solutions it requires additional components to implement a ground start compared to the integrated SL solution, which has on-chip controls for either ground or loop start. The Si3050 is a two-chip solution that includes a 20-lead TSSOP system-side device and a 16-lead TSSOP line-side device. Pricing for the chipset starts at $5.50 in quantities of 10,000. Samples are available now and volume production will begin in the third quarter of 2002. Evaluation boards are available for $175. Product brief: http://www.silabs.com/pdfs/3050_PB.pdf

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