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Analog Angle Article

Multichannel 16-bit, Gsps-class DAC targets base stations, slashes dissipation

Handsets get all the attention and glamour, but base stations are the vital backbone which makes wireless connectivity possible and increasingly ubiquitous. With the growth in networks and connectivity demands, there's been an increase in the number of base stations and also constraints placed on them, which translates to smaller, lower-power demands.

The DAC3484 multichannel digital/analog converter (DAC) from Texas Instruments targets these applications. This four-channel DAC not only is 25% faster than its nearest competitor, the vendor claims, but significantly cuts power consumption by 65% to 250 mW per channel—which means less input power needed, less heat to dissipate, and smaller packaging possibilities. [Note: they are also offering a two-channel version, the DAC3482.]

The 1.25 gigasample/sec (Gsps) DAC uses an interleaved digital input to reduce I/O pin count, reducing associated FPGA cost and simplifying track routing on the PC board (and if you prefer, the DAC is offered as the DAC34H84 with a wider input bus). It also includes a low-jitter 2x to 32x PLL to eliminate the need for an external PLL, as well as two numerically controlled oscillators (NCOs) for a lower interface rate and, again, a lower-cost FPGA. Key parameters such as offset, gain, group delay, and phase control are calibrated for improved performance and sideband suppression for wideband signals (closely related to group delay).

Unique internal packaging—invisible to the user—allows the IC to be housed in a 9×9 mm, multi-row QFN package for improved thermal performance, higher I/O density, and routing of tracks between pins.

Evaluation modules ($499) and reference designs, which include associated components for a complete bits-to-RF signal path and subsystem, are also available, plus IBIS models which facilitate verification of signal-integrity requirements.

Price and availability : All members of this family are sampling now, with production quantities available in the second half of 2011. The 9×9 mm four-channel DAC3484 is $58.60 and two-channel DAC3482 is 33.50 (1000 piece lots). The 12×12 mm DAC34H84, with a wider input bus, is $60.

For more information , click here ; the data sheet is available here .

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