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ADS1299-4: Regarding measurement of EEG using ADS1299 AFE

Sheik Abdullah P
Prodigy 50 points
Part Number: ADS1299-4
Other Parts Discussed in Thread: ADS1299

Hello everyone! The following is the schematic made for recording scalp potentials. In addition to the EEG amplifier, I have made a battery management system (figure 2) that could be used to boost up the 3.7 V of the Li-Po battery to 5 V (Voltage supply - AVDD to ADS1299).  The 3rd figure consists of LDOs to maintain a stable voltage supply to the EEG amplifier and other circuitry. Sometimes, I find everything to be working fine but sometimes I notice 22 Hz / 33 Hz and its harmonics in the PSD which are killing my signal of interest. I request the TI community to help me figure out the issue in the schematic. 

  • 0
    TI__Mastermind 19815 points

    Hi,

    I will try to get back to you by 3/8.

    Thanks

  • 0 in reply to ChienChun Yang
    Prodigy 50 points

    Hi Yang, I need your support to solve this issue

  • 0 in reply to Sheik Abdullah P
    TI__Mastermind 19815 points

    Hi,

    Sorry for the delay.

    -------------------------------

    For "sometimes I notice 22 Hz / 33 Hz and its harmonics in the PSD which are killing my signal of interest."

    May I ask what is PSD? 

    It's suggested to find out where the 22Hz/33Hz come from?

    e.g.

    And, they if you could bypass your power supply distribution circuit and use a cleaner power supply with LDO and to see whether same noise still present.

    Try internal test signal first with the same register configuration, see if the noises are there?

    " boost up the 3.7 V of the Li-Po battery to 5 V"  this may usually cause/generate some noises, so please probe and monitor this  AND the Vref voltage stability.

    See if you could boost higher  and then add an LDO?  Or, add a 5V to 5V LDO.

    ----------------------------------------------

    Are all parts from your Power supplies and distribution circuits from TI?

    We are not power supply and design experts, but if the root cause is found out to be from the Power distribution circuit, and you use all TI components for it, then you may open a ticket in the power supply sector/department if you are using all TI's parts in your power distribution circuit.

    -------------------------------------------------------------------

    Thanks