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ADC12D1600RF DES

Dan T
Prodigy 235 points
Other Parts Discussed in Thread: ADC12D1600

Is there a document that describes how to bring up an ADC12D1600 RF in DESIQ mode?

I'm currently doing the following:

1)  Set config register to DESIQ

2)  Put in test pattern mode and center the I and Q buses, together

3)  Perform internal calibration, with input terminated

4)  Sweep DES timing adjust.

I don't see the DES timing adjust doing anything for me.  Is there something I should do with it??

  • 0
    TI__Mastermind 20541 points

    Hi Dan,

    DES timing adjust is used correct the fixed timing skew offset between I and Q channel. The fixed timing skew should be adjusted to reduce spurs at Fs/2 – Fin spurs. The DES Timing adjust is programmed from 0d to 127d. By default DES timing adjust is set at 64d which may or may not coincide with local minimum.

    Please follow the procedure below.

    1. Select the DESIQ mode. The input signal must be applied to both I and Q differential inputs.
    2. Calibrate the ADC.
    3. Pick a frequency which is in the upper portion of the intended frequency range.
    4. Set the input power to approximately -1 dBFS.
    5. Perform an FFT on the output of the ADC and observe the spectrum and the magnitude of the timing error related spur at Fs/2 - Fin.
    6. Adjust the Register(7h) by changing Bits 15:9(default is set to 1000000).
    7. There will be a value which minimizes the magnitude of the Fs/2 spur and if you go beyond that value the spurs magnitude will start increasing again. The best register setting will be at the local minima.

    Regards,

    Neeraj Gill

    HSCC