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ADS1294R: Respiration

TOLSTOY R
Prodigy 10 points

Part Number: ADS1294R

Tool/software:

Team,

We are currently facing issues with the respiration waveform and suspect that noise coupling could be contributing to the problem.
We are using the ADS1294R analog front-end IC in our design.

Below are some key components used in the front-end section:

  • Multiplexer Part Number: MC14053BDG
  • Clamping Diode Used: BAV99LT1G
  • GDT Used: B88069X6241T902

Could you please provide your insights or recommendations on potential hardware improvements or best practices that could help address this issue.

  • 0
    TI__Guru 69186 points

    Hello Tolstoy,

    Thank you for your post.

    I'm not immediately familiar with those devices listed. Perhaps to begin debugging, can you try removing the diodes and GDT? And is there a way to bypass the multiplexer?

    Next steps would involve increasing the respiration TX current swing (RESP_MODP/N). Can you share the ADS1294R portion of your schematic as well as the register settings?

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Prodigy 10 points

    Hello Ryan,

    Thanks for your suggestions. Please find attached the ADS1294R portion of the schematics along with the register settings.

    Based on these details, please provide your inputs.



    RESP REG

    Bit

    7

    6

    5

    4

    3

    2

    1

    0

    Name

    RESP_DEMOD_EN1

    RESP_MOD_EN1

    RESERVED

    RESP_PH[2:0]

    RESP_CTRL[1:0]

    Set As

    1

    1

    1

    1

    0

    0

    1

    0

    CONFIG4:FREQ

    Bit

    7

    6

    5

    4

    3

    2

    1

    0

    Name

    RESP_FREQ[2:0]

    0

    SINGLE_SHOT

    WCT_TO_RLD

    PD_LOFF_CO 0 MP

    0

    Set As

    0

    0

    1

    0

    0

    0

    1

    0
  • 0 in reply to TOLSTOY R
    TI__Guru 69186 points

    Hello Tolstoy,

    Do you still need help with this issue?

    The schematic looks ok to me. The main difference I noticed is the value of R135 and R136 = 24.9k, which is less than the values used on our EVM (40.2k). This will increase the RESP_MOD current slightly, which is what I was recommending anyway if the received signal swing is too low.

    Can you share the results that you are observing in the current setup, as well as the rest of the device register settings? Also, what is the respiration amplitude and baseline impedance used in your measurements? Are you using a patient simulator for testing?

    Regards,

    Ryan