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Is it possible to configure the demodulator in AFE5809 to pass through ADC data to LVDS?

Dehuan Xin94
Intellectual 520 points
Other Parts Discussed in Thread: AFE5809

Hi, everyone,

I'm developing a AFE5809 + FPGA + Application SoC system.

The FPGA relies on the sync word in the LVDS channels of AFE5809 to function properly so I can not turn the demodulator off.

Is it possible to leave the demodulator enabled but let it pass ADC data through?

I'm thinking about:

set M=1; MODULATE_BYPASS 0x0A[14]=0; OUTPUT_CHANNEL_SEL 0x0A[11]=0; DWN_CNV_BYPASS 0x0A[2]=1

And set coefficient ram to a single impulse, and set profile RAM to a unit gain.

then ADC data will by pass down conversion, while decimation filter and decimation do nothing.

Is this correct?

So basically what I'm asking is, when down conversion is bypassed, is the ADC data passed unchanged to the I channel while Q channel is always 0?

  • 0
    TI__Mastermind 18285 points
    Dehuan,

    I'm assigning your post to the correct applications engineers. they should respond soon.
  • 0
    TI__Expert 6320 points

    Dehuan,

    Yes, if you want to bypass the DEMOD block, but keep the sync word,  please follow this configuration:

    EN_DEMOD =0

    DC_REMOVAL_BYP, DWN_CNV_BYP, DEC_BYP = 1

    M=1

    Modulate_Byp = 0 (enable to remove the sync word)

    Output_ch_sel = 0 (ch A)

    Thanks,

    Chuck

  • 0 in reply to Chuck Smyth
    TI__Genius 12025 points

    Hi Dehuan,

    According to your bypass settings for DC_removal, DWN_CNV and DEC.

    there is shown on the GUI:

    Then, First:

    1) Set the DEMOD block = ON

    Then, we tested and got the result (your signal + sync word):

    2) Set the DEMOD block = OFF

    Then, we tested and got the result (your signal + NO sync word):

    This just looks like only input signal without using Demod mode.

    Thanks and best regards,

    Chen

  • 0
    TI__Genius 12025 points

    Hi Dehuan,

    Here are the explanations of the setting to display Sync Word signal.

    1) Here is the AFE5809 register settings:

    2) After that when you are running TSW1400 GUI to the AFE5809 device,

    you should see the Sync Word showing including the capture data as well.

    One shows the captured data from CH3.

    The other shows the captured data from CH4.

    Thank you very much for using AFE5809 EVM and TSW1400 EVM.

    Best regards,

    Chen

  • 0 in reply to Chen Kung
    Intellectual 720 points
    Hello,

    I am trying to connect ADC output to FPGA for Image processing. The answer you provided will work for me as well?
    I will be getting signal from transducer which is around 200-300kHZ.
    Thank you
  • 0 in reply to Naik
    Intellectual 520 points

    It should work, but depending on whether you need sync word or not, there are two different ways to do it.


    This question is about the case when sync word is needed for FPGA to function properly, so we need data to pass through demodulator without demodulating it.


    If you don't need sync word, you can just bypass all of the demodulator chain, which is well documented in the reference manual.

  • 0 in reply to Naik
    TI__Genius 12025 points
    Hi Vatsal,

    The input signal for AFE5809 is using AC coupling method.
    Please let us confirm with our engineer to see your signal frequency from 200-300kHz range
    should be ok with those capacitor 0.1uF value can fit.
    We will let you know.

    Thanks and best regards,
    Chen
  • 0 in reply to Chen Kung
    Intellectual 720 points
    Hi Chen and Dehuan,

    Thank you,
  • 0 in reply to Chen Kung
    TI__Expert 6320 points

    Vatsal,

    Please see figure 59 from the datasheet.  I shows the low frequency roll-off.  INM Cap of 1uF is recommended for low-frequency applications.

    Thanks,

    Chuck Smyth