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Reconstruct the output signal of ADS1201

Riccardo Barbon
Prodigy 40 points
Other Parts Discussed in Thread: ADS1201, AMC1210, TMS320F28377D, DAC1220

Hi,

I bought an ADS1201 Delta-Sigma modulator for a medical applications. I'm trying to reconstruct the analog signal that enter to the device.

The input signals on the modulator have frequency that start from DC to 100Hz and have an amplitude from 0 to 5V. The output 1 bit stream of the modulator have frequency of 1MHz (the clock of the modulator).

After the modulator should be included a digital low pass filter which acquires only the useful signal and discards the quantization noise, in cascade a decimator to decrease the frequency and increase the number of output bits.

Exist an IC that I can connect in cascade of ADS1201 and obtain the 24 bit signal?

After that I have to reconvert the 24 bit to analog signal. What model of IC I can use for this operation?

Thank you in advance.

Riccardo

  • 0
    TI__Genius 9975 points

    Hello Riccardo,
    I am having a hard time understanding the motivation behind the process you want to implement… let me try to rephrase such process to see if I understood it correctly:
    1)    Your input signal is 0 V to 5 V with frequency components between DC and 100 Hz.
    2)    You would like to acquire such signal with a delta sigma modulator (ADS1201).
    3)    Then you would like to filter the delta-sigma modulator output to obtain  24-bit wide codewords.
    4)    Then you want to take such 24-bit codewords and reconstruct the original analog signal.
    Are you performing any digital signal processing onto the 24-bit codewords coming out of the digital filter? Otherwise it would seem to me that you can accomplish the task by using purely analog blocks (op-amps).


    To answer your questions:
    The AMC1210 and TMS320F28377D can be used to filter the ADS1201 output.
    The TMS320F28377D has 12-bit digital to analog converters that you could use to put out an analog signal. Another option is to use something like the DAC1220.


    Hope this helps.


    Best regards,


    Jose

  • 0 in reply to Jose Duenas
    Prodigy 40 points
    Hi Jose,
    thank you for your answer. The points that you wrote are all correct.
    I'm working on a thesis project of an EEG.
    The current aim is to verify that the conversion of the Delta Sigma doesn't introduce additional noise to the signals that are extract from electrodes. I don't need to perform operations on the digital signal.
    Do you think that the configuration op-amp can break into further noise in the signal?
    What kind of configuration do you recommend to take with op-amp?
    Once you converted the signal I'll have to check that this is the same compared to the original input signal.
    Thank you in advance.
    Best regards,
    Riccardo
  • 0 in reply to Riccardo Barbon
    TI__Genius 9975 points

    Hello Riccardo,

    You are very welcome.

    The op-amp, INA or any other circutiry used will indeed add noise to the signal; however, without any amplification, the EEG signals could not be processed or acquired an any meaningful way.

    My suggestion would be to search through our forums for ECG, EEG related posts. You will find a lot of information.

    For example:
    e2e.ti.com/.../826893
    www.edn.com/.../Use-Spice-to-analyze-DRL-in-an-ECG-front-end
    e2e.ti.com/.../702489
    e2e.ti.com/.../1464
    e2e.ti.com/.../394435

    Hope this helps.

    Best,

    Jose