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16bit dual-channel DAC aims at 3G/4G comms

Posted: 25 Apr 2008 ?? ?Print Version ?Bookmark and Share

Keywords:DAC? 3G? 4G? TD-SCDMA? WiMAX?


Texas Instruments Inc. has introduced a 16bit, dual channel, 800MSps transmit DAC solution designed for wireless base stations, software-defined radio applications and multi-frequency test equipment. The DAC5688 expands on TI's portfolio of full-featured DACs and represents a 67 percent space reduction over the previous generation. Offered in a space-saving 64-pin 9mm x 9mm QFN package, the DAC5688 features enhanced performance to support existing 3G applications, including W-CDMA and TD-SCDMA, and emerging 4G applications, including WiMAX and LTE. For instance, for an output frequency of 70 MHz, the device achieves 81dBC ACLR for a single-carrier W-CDMA application.

Smart chip
To further enhance performance in communications design, the DAC5688 allows for more exact frequency placement, superior linearity, noise crosstalk and PLL phase noise performance. An optional frequency mixer with a 32bit numerically controlled oscillator (NCO) runs up to 800MHz, enabling more exact frequency placement. A digital inverse SINC filter compensates for natural DAC sin (x)/x frequency roll-off. In addition, the digital quadrature modulator correction (QMC) feature allows IQ compensation of phase, gain and offset to maximize sideband rejection to create a flatter pass band. An integrated 2x-32x clock multiplying PLL/VCO offers lower jitter and four times the multiplying range over the DAC5687. This extended range can enable designers to operate with simpler external clocking, reducing complexity and cost.

To increase flexibility, the DAC5688 dual CMOS data bus provides 250Mbit/s input data transfer per DAC channel. Several input data options are available including dual-bus data, single-bus interleaved data, even and odd multiplexing at half-rate, and an input FIFO with either external or internal clock, which eases interface timing. Input data can be interpolated two, four or eight times by on-board digital interpolating FIR filters with greater than 80dB stop-band attenuation.

Tools, support
TI offers a suite of easy-to-use evaluation modules (EVMs) and tools to speed development time. With the inclusion of the TRF3703 single-chip quadrature modulator and CDCM7005 clocking distribution chip, the DAC5688 EVM allows for rapid prototyping of high performance, space efficient, transmit signal chain solutions.

In addition, the TSW3100 digital pattern generator's CMOS outputs provide an evaluation platform to enable designers to realize the increased system performance provided by the new device's wide bandwidth. These include improved power amplifier linearization for digital pre-distortion (DPD) solutions with TI's GC5322 single-chip transmit processor solution, reduced cost of infrastructure, covering wide bandwidth with one implementation, implementation of more standards in SDRs and advanced system performance for test and measurement.

To further simplify design, reduce development costs and speed time to market, TI offers a wide variety of devices to complete the signal chain, including operational amplifiers (OPA695) and an integrated PLL/VCO (TRF3761).

The DAC5688 is available now in 64-pin QFN package and is priced at $29.95 in 1,000-piece quantities. Samples and EVMs are available.

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