JAJSSV2G March 2011 – January 2024 DAC3482
PRODUCTION DATA
The DAC3482 has a full complex mixer (FMIX) block with a Numerically Controlled Oscillators (NCO) that enables flexible frequency placement without imposing additional limitations in the signal bandwidth. The NCO has a 32-bit frequency register (phaseadd(31:0)) and a 16-bit phase register (phaseoffset(15:0)) that generate the sine and cosine terms for the complex mixing. The NCO block diagram is shown below in Figure 6-22.
Synchronization of the NCOs occurs by resetting the NCO accumulators to zero. The synchronization source is selected by syncsel_NCO(3:0) in config31. The frequency word in the phaseadd(31:0) register is added to the accumulators every clock cycle, fDAC. The output frequency of the NCO is:
With the complex mixer enabled, the two channels in the mixer path are treated as complex vectors of the form IIN(t) + j QIN(t). The complex signal multiplier (shown in Figure 6-23) will multiply the complex channels with the sine and cosine terms generated by the NCO. The resulting output, IOUT(t) + j QOUT(t), of the complex signal multiplier is:
where t is the time since the last resetting of the NCO accumulator, δ is the phase offset value and mixer_gain is either 0 or 1. δ is given by:
The mixer_gain option allows the output signals of the multiplier to reduce by half (6dB). See Section 6.3.7.3 for details.