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Interfacing ADS4122 to TMS320C6748

Shanguo Lu
Intellectual 570 points
Other Parts Discussed in Thread: ADS4122, TMS320C6748

Hi,

I am thinking of interfacing ADS4122 to TMS320C6748 DSP for an IF application. It is desirable to sample at about 20~25MHz, 12bit.

The data will be sampled at 20MHz, continuously stream. If we could use DMA, a repeated transfer with DMA buffer size of 1024 (that's about 50us) will be great. Upon DMA interrupt of 1024pts, we'd like to FFT 1024pts using the DSPLIB, I think the FFT may complete within a short 15kcycles (32us if 456MHz?). 

From wiki, it seems possible for the uPP interface to achieve this data transfer rate, possible upto 60MSPS for 12b ADC. 

Mode Theoretical (MB/s) Realistic (MB/s)
1 Ch, 8-bit 75 60
1 Ch, 16-bit 150 120

I would to find out from here that,

1) Is my setup realistic? Can the C6748 interface to ADS4122 @ 20MSPS via DMA?

2) Will 1024pts FFT operation be fast enough and complete within such short period (32us)?

3) Is the internal RAM sufficient, as the data block is small size? Do you think if I need to include LPDDR SDRAM?

I am targeting a battery operated device, so power consumption is the main concern; thus limit the processor. I think the next choice may be FPGA, but I prefer not to go that path.

Thanks and regards,

Shanguo

  • 0
    TI__Mastermind 35645 points

    Hi,

    Thanks for your post

    I believe, your specification should suit for C6748 to interface to ADS4122 @20MSPS but these devices would most well-suited for multicarrier,

    wide bandwidth communications applications.

    The sample design requirement below would be best suited  for ADS4122

    Sampling rate                                          ≥ 122.88 Msps

    Input frequency                                      > 125 MHz to accommodate full 2nd nyquist zone                            

    Input full scale voltage                         2 Vpp

    Overload recovery time                       < 3 clock cycles                                    

    Digital interface                                     Parallel LVDS

    Power consumption                            < 200 mW per channel         

    For selection tree of high speed ADC's , you could see the below link:                   

    http://www.ti.com/lit/sg/slyb183a/slyb183a.pdf

    Just look into it. For more details, if you could post your queries to high speed data converters forum would be most recommended.

    Thanks & regards,

    Sivaraj K

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  • 0 in reply to Sivaraj Kuppuraj
    Intellectual 570 points

    Thanks for your prompt advice.

    Yes, C6748 has uPP interface that can be used to interface to ADS4122. And I am concerned that if C6748 is good enough for interfacing to ADS4122 or its equivalent. I thought it is most relevant in this forum instead.

    Maybe we shall wait for other forum members' opinion.