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TI DAC supports four WCDMA carriers at half the power

Posted: 07 May 2003 ?? ?Print Version ?Bookmark and Share

Keywords:texas instruments? dac5686? dual dac? programmable dac? digital analog converter?

The DAC5686 programmable dual DAC of Texas Instruments (TI) Inc. supports up to four WCDMA carriers, while consuming half the power of comparable solutions. The DAC also offers designers with three modes of operation and clock modes, and allows a low input data rate with a programmable interpolation rate of 2x to 16x up to an output rate of 500MSa/s.

Offered in a 100-pin TQFP, the IC exhibits an ACPR >68dBc (122.88MHz) for single carrier WCDMA signals and an ACPR >71dBc (61.44MHz) for dual carrier WCDMA signals. It operates from 1.8V digital/3.3V analog supply and dissipates <400mW. Current output ranges from 2mA to 20mA.

The DAC5686 can be used in three clock modes - PLL, DAC, and Data/DAC clock modes - and in three modes of operation - dual channel, quadrature modulation, and single sideband upconversion.

Dual channel mode is used for baseband modulation or a two-channel digital IF system. The dual DACs and datapaths operate independently. The interpolation filters increase the DAC update rate, resulting in reduced sin x/x roll off and relaxed requirements for analog post-filtering.

Quadrature modulation mode converts a complex digital baseband signal to IF frequency after upsampling. It is Used for IF >50MHz. Single sideband upconversion is used when a complex IF output allows offset of signal after analog quadrature modulator, placing LO feedthrough and unwanted sideband signal out-of-band.

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