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Data Converters for Advanced Digital Communication Applications

Thu, 08/30/2001 - 9:28am
Analog Devices announced two analog-to-digital converters (ADCs) that enable intermediate frequency (IF) sampling for simpler, lower-cost and more reliable design of broadband, wireless, and other advanced digital communications applications. The AD9433 and AD9235 reinforce ADI's commitment to supporting IF sampling architectures as the company's continuous innovation enables elegant, cost-efficient designs for new wireless standards such as W-CDMA, CDMA2000 and GSM/EDGE. Analog Devices has demonstrated its commitment to simplifying wireless design by developing products for other areas of the IF signal chain. Examples include the recent development of the VersaCOMM™ family of re-configurable digital converters, which perform digital filtering and frequency conversion, and the company's TxDAC® series of high-performance, low-power CMOS digital-to-analog converters (DACs).

The AD9433 is a 12-bit ADC, with a sampling rate of 125 mega samples per second (MSPS), which is capable of IF sampling input frequencies as high as 350 MHz. An IF sampling radio architecture eliminates an analog down-conversion step, thus simplifying design, reducing system cost, and improving the reliability of the radio front-end. The AD9235 is a new member of ADI's portfolio of low-power data converters and is the industry's first 12-bit, 65 MSPS ADC that uses a 3 V (2.7 V to 3.6 V) voltage supply for IF sampling up to 100 MHz in small or portable applications, such as pico-cell cellular base stations.

The AD9433 is a 12-bit 125 MSPS ADC with an on-chip track-and-hold circuit optimized for maximum dynamic performance in wideband and high IF carrier applications such as GSM cellular base stations. The device requires only a 5V supply and a differential encode clock, and is capable of directly sampling IFs up to 350MHz. No external reference or driver components are required for many applications. In addition, the part is pin-compatible with the AD9432 breakthrough 12-bit 105MSPS ADC for simple system upgrades.

A user-selectable, on-chip proprietary circuit optimizes spurious-free dynamic range (SFDR) versus signal-to-noise-and-distortion (SINAD) ratio performance for different input signal frequencies, providing as much as 85 dBc SFDR performance over the dc to 125 MHz band. The encode clock supports either differential or single-ended input and is PECL compatible. The output format is user-selectable for binary or two's complement and provides an over range (OR) signal.

The AD9235 is a 3 V 12-bit 65 MSPS ADC with an on-board, programmable reference designed for applications in which the combination of the highest dynamic performance and low power dissipation is a key requirement. It is also the industry's lowest-power converter for IF sampling applications up to 100 MHz. Its 84 dBc SFDR with a full Nyquist input signal enables IF sampling architectures in applications such as portable digital communications systems, and battery-powered instrumentation equipment. The outstanding signal-to-noise (SNR) of 70dBc, and a power dissipation of only 300 mW, makes the AD9235 well suited for power-conscious applications, such as transportable ultrasound imaging equipment.

The AD9235 contains a patented input sampling network, voltage reference, multistage differential pipelined architecture and output error correction logic. The innovative design allows the AD9235 to achieve 12-bit accuracy and guarantee no missing codes over its full operating temperature range while achieving low power dissipation. The AD9235 accepts a single-ended or differential input signal, with a 500 MHz input bandwidth. A clock duty-cycle stabilizer allows the device to maintain its rated performance over a wide range of clock pulsewidths, particularly useful in portable and battery-operated applications where the clock source may be less than ideal.

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