Analog Devices, a global provider in high-performance semiconductors for signal processing applications, today announced the industry's first IC that integrates four high-performance data converters on a mixed-signal front-end chip for broadband applications. The AD9862 is optimized for wireless broadband applications, which can deliver next-generation services, such as high-speed web access, interactive gaming, and video on-demand -- services that require equipment using data converters with increasingly higher resolutions and data rates. The chip's high level of integration and performance features greatly reduce board space and cost, two of the most pressing challenges for manufacturers of broadband equipment. Wireless broadband applications typically require complex modulation, error correction and signal-combining technology to overcome noise and environmental interference. The AD9862 provides the performance required to handle these techniques, along with communications-specific digital processing and several auxiliary functions that facilitate their implementation.

The AD9862 is a member of ADI's family of Mixed-Signal Front End (MxFE) ICs, which is based on the company's "smart partitioning" methodology, a mixed-signal design philosophy that partitions the signal path according to performance, rather than along analog/digital, boundaries. The AD9862 is the most highly integrated device in the MxFE family. One chip integrates two 12-bit 64-MSPS analog-to-digital converters (ADCs) and two14-bit 128-MSPS digital-to-analog converters (DACs), delivering a level of performance currently available only with discrete components. Also available is a lower resolution version of this chip the AD9860 that integrates dual 10-bit ADCs and 12-bit DACs for lower cost, less demanding applications. These devices are the first integrated solutions to provide this level of performance; the AD9860 and AD9862 meet both the cost requirements of subscriber equipment and the high-performance requirements of base station and head-end infrastructure applications.

"Wireless broadband is an emerging application posing complex analog design challenges, due to the unpredictable nature of the wireless channel and the need for high data rates," said Dave Robertson, product line director, High Speed Converters Group, Analog Devices, Inc. "With the AD9862, engineers can implement a transceiver with the complex image rejection architecture required for wireless broadband with fewer chips, less board space and lower cost."

The AD9862 is a versatile, integrated mixed-signal front end that is optimized for the broadband fixed wireless access market. The transmit path accepts a variety of data formats and includes dual high-performance DACs, programmable gain amplifiers (TxPGA), 2x or 4x interpolation filters, a digital Hilbert filter and digital mixers for complex or real-signal up-conversions. These features support a system architecture that substantially reduces reconstruction and anti-alias filtering requirements.

The AD9862 receive path includes dual high-performance ADCs that can be used to receive diversity or in-phase and quadrature (I&Q) data at baseband or low intermediate frequencies (IF), input buffers, programmable gain amplifiers (RxPGA) and decimation filters. The AD9862 also contains a programmable delay locked loop (DLL) clock multiplier integrated timing circuits that allow the use of a single reference clock and auxiliary ADCs and DACs for use in the monitoring and control of receive signal strength indication (RSSI) functions, temperature sensors, and gain and offset adjust circuitry.

Analog Devices, Inc., 804 Woburn Street, Wilmington, MA 01887. Tel: 1/800-ANALOGD (262-5643); Fax: 781-937-1021; http://www.analog.com

The broadband market is showing signs of maturing because more manufacturers are jumping in and they want to go after niche markets where they can differentiate their products. These manufacturers of products like set-top boxes want chips that will help them achieve their goals. Unfortunately, some of the very highly integrated chips won't let them tweak their designs so their products stand out in the market.

The AD9860 and 9862 is a concept and IC from Analog Devices that helps broadband product suppliers stand apart from their competitors. It promises to logically separate the analog and digital designs so you can shrink your overall design, the bill of materials, and get to market on time.

ADI believes that the broadband and the home network markets are driving each other and the time is right for improved design processes. ADI's mixed signal front end products use something they call smart partitioning. It is a design philosophy that partitions the system along the lines of performance, rather than along the lines of analog and digital boundaries, or by integrating everything on a single chip. Hence, you get to differentiate your product.

ADI is focused on power line networking, phone line networking, and wireless access. According to the company, smart partitioning can help reduce the total silicon area. For example, as designs migrate from 0.35 micron to 0.25 micron, which may be close to the smallest that designs can go because of the demands on the analog performance in these devices. The analog design shrinks by 29% in that process transition. However, digital circuitry typically shrinks by about 50% because you generally gain a greater reduction in digital circuitry. However, you are still limited to the amount that you can reduce your total silicon area because of the requirements to have analog on a larger process. ADI decided that it was time to look at the design picture in a more holistic manner. Instead of trying to integrate all the analog and digital, they try to logically separate the VLSI digital from the mixed signal functions. So when your digital designs shrink from 0.35 micron to 0.13 micron, it results in a large area of reduction and possibly a cost savings.

I know what you're thinking, ADI is just trading one set of challenges for another by separating the analog and digital. But their concept of smart partitioning doesn't strictly separate the digital from the analog, but separates the system in a way that makes the most sense. For example, you wouldn't want to have a 300MHz bus just to separate the analog and digital. By minimizing the digital to just the digital circuitry that makes sense on the mixed signal front end and leaving the high-speed VLSI digital in the digital chip, you can get the best of both worlds. Also, if you want to put some analog circuitry onto a chip that requires a bipolar, SiGe, or other process, then you really don't have a choice - you need to separate the digital from the analog and mixed signal. ADI carves up the customer's system and does an analysis, looking at where they should separate the system from an IC perspective. Key points include how to partition the system to get the required performance at the right power and price point.

The concept of smart partitioning is not new to ADI; they use it for their AD9873 to fit into a set-top box. It performs all the mixed signal functions leading out to the tuners and the other functions of high performance, high frequency analog. The newly introduced AD9860 is a mixed signal front-end designed for broad band wireless communications. It is a mixed signal front-end processor with dual converter receive and dual converter transmit paths. The difference between the AD9860 and AD9862 is in the resolution of the converters. The former has 10-bit ADCs and 12-bit DACs and the latter has 12-bit ADCs and 14-bit DACs. Both devices have internal or external references, input buffers, programmable gain amplifiers, decimation filters, and a digital Hilbert block on the receive path. All of this helps with an image rejection architecture.

Similarly on the transmit path it features programmable full scale output current, independent gain and offset control, a digital Hilbert interpolation filters, clock distribution blocks, programmable output clocks, a SPI port for programming registers, and auxiliary ADC and DAC functions. Auxiliary DACs are good for automatic gain control; the ADCs could be used for measuring signal strength, and temperature monitoring.

The Hilbert filtering produces a phase shift so a customer with an existing digital ASIC on the transmit path that is capable only of outputting real data, can input the data into the 9860. The digital Hilbert filter is used to introduce the phase shift so you have I and Q signals needed to implement the image rejection architecture. The Hilbert filter generates a complex signal from a real signal, which allows you to put it into an image reject mixer, eliminating the high or low side image. That eliminates some of the filtering requirements and in turn reduces the overall cost to the overall system. Because the 9860 and 62 convert the signals to digital and can handle complex or real signals, customers are able to do proprietary digital back-end design.

In applications such as a typical broadband modem, the AD9862 acts as a bridge between the high-frequency RF circuitry and the digital circuitry. In the case of the broadband wireless applications where the radios are in the gigahertz range, you need to have an RF/IF stage interfacing to the 9862, but it could also be used for direct conversion as well, to handle an input bandwidth up to 80 MHz.

The image reject architecture used by ADI allows you to optimize and reduce the local oscillator feed through. In the company's device the gain and offset use DACs on each of the converters so the customer can optimize and tune their system through each of those converters in the image reject system. Those are added features that you wouldn't know about unless you looked at the register maps. It's just too complex to put on any block diagram.

The 9860 and 9862 are connected to a quadrature upconverter and need no active level shifting components because of the gain and offset outputs. Additionally, only simple passive filters are required. So filtering requirements are eliminated, and in many applications you may only need a simple passive filter on the output.

Pricing and Availability

The AD9862 is sampling in a 128-lead LQFP (low-profile quad flat package) and is priced at $15.50 per unit in 100,000-unit quantities. The AD9860 is sampling in a 128-lead LQFP (low-profile quad flat package) and is priced at $9.00 per unit in 100,000-unit quantities.