Analog front ends beat a speedy path to integration

With high-quality front-end processing for data, communications, and imaging (still and real-time) systems becoming more critical, designers are fast beating a path to secure analog front ends (AFEs) with higher speed and lower jitter for TV and home theatre applications, better signal conversion topologies for high-definition imaging, higher sensitivity for various wireless authentication systems, greater intersystem compatibility, and faster time-to-market. A snapshot of the latest devices shows that the solution to a better AFE stage (conversion of a raw analog input into basic digital form, which is followed by digital processor stages that may or may not be part of the AFE as such; and with the AFE often with digital-to-analog capability) is to integrate at ever-higher levels to cut signal-path lengths between interfaces and to minimize the number of external components and board real-estate.

For the commercial datacom/telecom infrastructure, PMC-Sierra's (Santa Clara, Calif.) PM4380/4381 stand alone AFE is suited to very high data rate DSL (VDSL2) and asymmetric DSL (ADSL2+) customer premises equipment (CPE). Touting low transmit-path distortion and noise floor, and precision 16-bit data converters claiming best-in-class performance for both transmit and receive, the PM4380 (for VDLS2) cites extended rate/reach performance. The low-noise floors on transmit and receive along with integrated programmable receive equalizer and filters minimize the need for complex, external filters.

The company's PM4381, which is pin-compatible with the PM4380, is suited to ADLS2+ designs. It interfaces directly with the company's MSP7120 prcoessor to provide a complete chipset for advanced residential gateways and integrated access devices (IADs). Both devices implement the company's ADSL2+/VDSL2 interface specification (AVIS) digital interface, which simplifies connection to a variety of DSL processors by offering selectable data rates, clocking modes, and control signaling.

Maxim's (Sunnyvale, Calif.) newest and previously unannounced devices include two families of AFEs, their MAX19710 to MAX19713 (in four versions) 7.5 to 45 Msps devices for wideband communication applications operating in full-duplex mode; and their 10-bit MAX19706 (22 Msps) and MAX1907 (45 Msps) half-duplex devices. Both are optimized for low-power portable applications. The MAX19713 integrates a dual 10-bit 45 Msps receiver ADC, dual 10-bit 45 Msps transmit DAC, three fast-settling 12-bit auxiliary DAC channels for ancillary RF front-end control, a 10-bit 333 ksps housekeeping auxiliary ADC, and uses two independent 10-bit high-speed parallel buses. The MAX19706 and MAX19707, with the same functionality, shares a high-speed digital bus.

In the consumer area, Intersil's (Milpitas, Calif.) ISL98001 triple-channel analog front end for TVs, monitors, home theater and business projectors incorporates all of the functions needed to digitize YPbPr video signals and RGB graphics signals from DVD players and VCRs. The three-channel, 8-bit device is available in five speed grades (140 to 275 Mpixels/s) to support HDTV resolution and computer monitor resolutions up to QXGA. This device includes automatic black level compensation circuitry to accommodate the lowest-cost home theatre systems, and eliminates the need to calibrate the luminance and color offsets during the manufacturing phase.

Also boosting the integration level to extend flexibility, Toshiba America's (San Diego, Calif.) TB1311AFG is a combination programmable audio/video and component switch that accepts all standard analog audio and video signals for digital TV, set-top boxes, and other audio/video products. Previously, the company offered audio/video switches and component switches as separate products. The device's audio block, with three outputs, accepts up to 10 inputs. The programmable video block can accept composite, S-video, component, RGB, and SCART signals. Other features include an automatic sync processor, real-time format detector that supports display of high-resolution component video, and a no-signal input detector that activates a dummy HD/VD signal output to stabilize the TV picture output.

Analog Devices' (Norwood, Mass.) AD9970 for high-definition image/video processing for camcorders and digital still cameras has a reported industry-first low-voltage differential signaling interface, which is said to boost signal conversion performance by 30 percent. The AFE includes a 14-bit ADC, a variable gain amplifier (VGA), and correlated double sampler. Its programmable timing driver boasts precise control of clock signals to further enhance performance.

Fingerprints and footprints
Bringing extra intelligence to AFEs, Microchip's (Chandler, Ariz.) first analog front end for low-frequency (typically 125 kHz) wireless authentication applications is said to provide industry-best sensitivity and programmable antenna tuning for microcontroller-based systems. The MCP2030 , for such applications as monitoring of tire pressure, RFID, keyless entry, and hands-free apartment door access, is a three-channel transponder AFE that provides adjustable modulation depth down to 8 percent. Sensitivity is 3 microvolts p-p. This device includes an intelligent wake-up filter section that keeps the external microcontroller in low-power mode until the chip detects a recognized input signal.

While highly integrated chips rule, component-style AFEs can sometimes deliver an edge, particularly in medical applications. Analog Devices' AD8334 quad variable-gain amp and its 10-bit AD9219 and 12-bit AD9228 A/D converters, for instance, are particularly suited to ultrasound imaging. The AD8334 has a 101 dB signal-to-noise ratio at 5 MHz, which is twice the SNR of competing devices, according to the company. The 10-bit AD9219 quad ADC, and the 12-bit AD9228, both available in 40- and 65- Msamples/s speed grades, achieve a 70 dB SNR and 82-dB spurious-free dynamic range (SFDR).

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