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ADS1299: ads1299 design peobelm

ian wu
Intellectual 775 points
Part Number: ADS1299

Tool/software:

hi

we have a project for EEG signal acquisition. We use two ADS1299 chips and expand the original 16 channel acquisition channel to 256 channels through an external analog switch chip. This means that each ADS1299 analog channel is connected to a 16/1 analog switch. The expansion of 16 acquisition channels to 256 acquisition channels is achieved through synchronous high-speed switching of front-end analog switches.

May I ask if this application plan is feasible? Can the ADS1299 chip support such applications? Can the acquisition quality of 256 EEG signals be guaranteed?

  • 0
    TI__Guru 66386 points

    Hello,

    Thank you for your post. 

    How often is the external MUX switching? Is it switching to a new input electrode after every ADC sample? Or do the inputs remain constant and are sampled for a duration of time before changing the external MUX to measure other electrodes?

    Generally, adding an external mux is not favorable because:

    1. Each time the mux switches, it produces a transient input voltage, which takes 3 samples to fully settle and reduces your effective data rate. The settling time required by the integrated digital sinc3 filter. 
    2. Impedance mismatch through the switches (switch resistance, parasitic capacitance, leakage current, etc.) can introduce unwanted offsets and degrade CMRR

    Can you share who is the end customer? Let me know if you would like to continue the conversation offline.

    Regards,

    Ryan