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DAC5687

ruchi johari
Prodigy 190 points
Other Parts Discussed in Thread: DAC5687

Hi

We are using DUC GC5016---> CFR  GC1115---->DAC5687 in our transmit chain.

The CFR input is complex, one channel parallel IQ and output is one channel ,complex with OUT_A = I sample from channel  A   and OUT_B= Q sample from channel A.

The DAC is connected such that CFR's OUT_A is routed to DAC A port and OUT_B is routed to DAC B port  with register  interl = 0.

We are taking DAC Output from IOUTA1/IOUTA2 only, we are not using the IOUTB1/B2

My question is since our CFR output is parallel IQ going separately to the DACA and DACB ports, how does output appear only at IOUTA1/IOUTA2 port. I believe the DACA and DACB chains are independent and would process only the data available on their indiviual ports. By this logic input I data should be processed by DACA chain and appear only at IOUTA1/A2 whereas Q data processed by DACB chain appearing only at IOUTB1/B2 but then how do we get the output at only IOUTA1/IOUTA2 port?

  • 0
    TI__Genius 17340 points

    Ruchi,

    First to clarify.  You are applying your I and Q patterns to data inputs A and B respectively. You then want the DAC to output the combined signal at the IOUTA port?

    The DAC takes in your I and Q data through data inputs A and B.  The DAC then outputs the corresponding analog signal at IOUTA and IOUTB respectively. The I and Q signals should then be fed into the I and Q inputs of an IQ modulator, which will eliminate the unwanted sideband from the modulated output. The DAC does not do this combination itself, nor would it need to, since the sideband is a product of modulation rather than digital to analog conversion.

    Regards,
    Matt Guibord

  • 0 in reply to Matt Guibord
    TI__Genius 17340 points

    Ruchi,

    Sorry for the confusion, it seems that I have misinterpreted the question.  It seems that you are inputting I and Q data into the two channels and the output is only at A, but you expect it to be at A and B.  Check to make sure that you are not accidentally putting the DAC into half_rate mode (register 0x04 bit 5).  In this mode, the DAC will multiplex the data from channels A (even samples) and B (odd samples) and output them on IOUTA only.  If you are not sure if you have set this mode, send me your DAC settings and I'll take a look.

    Regards,
    Matt Guibord