The DAC5687 is a dualchannel 16bit highspeed digitaltoanalog converter (DAC) with integrated 2×, 4×, and 8× interpolation filters, a complex numerically controlled oscillator (NCO), onboard clock multiplier, IQ compensation, and onchip voltage reference. The DAC5687 is pin compatible to the DAC5686, requiring only changes in register settings for most applications, and offers additional features and superior linearity, noise, crosstalk, and phase-locked loop (PLL) noise performance.
The DAC5687 has six signal processing blocks: two interpolate by two digital filters, a finefrequency mixer with 32bit NCO, a quadrature modulation compensation block, another interpolate by two digital filter, and a coarsefrequency mixer with Fs/2 or Fs/4. The different modes of operation enable or bypass the signal processing blocks.
The coarse and fine mixers can be combined to span a wider range of frequencies with fine resolution. The DAC5687 allows both complex or real output. Combining the frequency upconversion and complex output produces a Hilbert Transform pair that is output from the two DACs. An external RF quadrature modulator then performs the final single sideband upconversion.
The IQ compensation feature allows optimization of phase, gain, and offset to maximize sideband rejection and minimize LO feedthrough for an analog quadrature modulator.
The DAC5687 includes several input options: singleport interleaved data, even and odd multiplexing at half rate, and an input FIFO with either external or internal clock to ease the input timing ambiguity when the DAC5687 is clocked at the DAC output sample rate.
