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TMS320F28335 MULTIPLE ADC convertions at same time!

Vanderley Maia
Prodigy 180 points

Hi everyone,

 

I need to convert 10 signals at same time and after that to process into the DSP,

I have two options:

 

1) Using 10 sample and hold, all the sample hold will sampling their signals at the same time, after the Sample Hold finish the DSP will convert

each sample one after one, my question is, wich Sample Hold to use?

 

2) Using 10 ADC converters with 1 channel. after all ADC finish the convertion the DSP will get the data, by one bus I2C or SPI. My second question wich ADC module to use?

 

P.S. I need to get all signals at same time at 1khz rate.

 

Thanks!

  • 0
    TI__Guru* 82680 points

    Vanderlay,

    I know your question is on external circuit to achieve this, but I am interested to understand why the internal ADC cannot be used.  Other than the obvious that there is only 2 sample and holds, so only 2 channel simultaneous sampling is supported; if you look at your data rate of 1kHz vs the effective delta between sampling 10 channels in 5 groups of 2(600ns skew) this is quite low.

    So shouldn't the BW of the input signals be slow enough to allow 600ns/1ms sampling time delta?  Just curious on the system limitation in this case; trying to save some system BOM for your application.

    Best,

    Matthew

  • 0 in reply to MatthewPate
    Prodigy 180 points

    Hi Matthew,

    Well I'm developing a 3 phase filter active.

     

    Sorry not 1kHz, I will use a 10kHz trigger.

     

    Assuming that I'm using the rate convertion of the ADC in 12.5Mhz, than 80nS/sample

    I need make 10 convertions (each [1/10000] s), than I will have almost 700nS between the first and the last convertion.

    I'm monitoring voltage and current signals, and I will make the control of my filter according to the results of the AD convertions

     

    I think that this isn't problem (the 700nS delay), but my teacher wants to do all the convertions at same time, in the worst case he wants to do all the

    sample and hold at same time and after that make the convertion using the DSP ADC module, but in this case

    all the samples were get at same time.

     

    Well I will make one test tomorrow, I need to check, if using the ADC in a 12.5Mhz rate I will have disturbances in the signals.

  • 0 in reply to MatthewPate
    Prodigy 180 points

    And Thanks :D

     

    Best regards!