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AFE4404: Transitory response never stabilizes

Part Number: AFE4404

Hello, 

I am reading a static measure with the AFE4404, but the signal never stabilizes. I am using these configuration: Rf = 1M ; Cf = 5 pF ; Led Current = 30 bits. 

I already tried to modify parameters and timing engine but the transitory response holds. 

Do you have any suggestions?

Thank you,

Ana Maria.

  • Hello Ana,

    Welcome to TI e2e forum!

    Regarding your query, verify your configuration settings on the AFE4404 EVM and confirm if your register settings are valid.

    If you see similar response on the EVM, please share your configuration and test measurement results for further debug.

  • Hello Praveen, 

    I am using these configuration:

    3 times average;

    TIA gain = 6;

    Cf = 0;

    Led current = 30;

    Internal clock;

    LED2 start = 0; LED2 end = 399;

    Sample LED2 start = 80 ; Sample LED2 end = 399;

    ADC reset phase 0 start = 401; ADC reset phase 0 end = 407;

    LED2 convert phase start = 408; LED2 convert phase end = 1467;

    LED3 start = 400; LED3 end = 799;

    Sample LED3 start = 480 ; Sample LED3 end = 799;

    ADC reset phase 1 start = 1469; ADC reset phase 1 end = 1475;

    LED3 convert phase start = 1476; LED3 convert phase end = 2535;

    LED1 start = 800; LED1 end = 1199;

    Sample LED1 start = 880; Sample LED1 end = 1199;

    ADC reset phase 2 start = 2537; ADC reset phase 2 end = 2543;

    LED1 convert phase start = 2544; LED1 convert phase end = 3603;

    Sample Ambient1 start = 1279; Sample Ambient1 end = 1598;

    ADC reset phase 3 start = 3605; ADC reset phase 3 end = 3611;

    Ambient1 convert phase start = 3612; Ambient1 convert phase end = 4671 ;


    pdn cycle start = 5471;

    pdn cycle end = 39199;

    PRPCT = 39999;

    Any idea? 

    Thank you.

  • Hello Ana,

    Like I had mentioned in the previous post, you can verify your configuration settings on the AFE4404 EVM and confirm if your register settings are valid.

  • Hello Praveen,

    I don't have the AFE4404 EVM because I have my own PCB.

    I know that conections are correct because I can obtain the pulseoximetry wave (Figure 1) with a 880 nm LED. However, the signal has a base line variation.

    Do you have any idea of what is causing the transitory response? 

     

  • Hi,

    To check if the transitory behavior is from the sensors, use PD_DISCONNECT mode to disconnect the PD from the TIA and perform the experiment.

    If it is from the sensors, AFE will not be able to help reduce the baseline drift. You may want to look at implementing some filtering in post processing.