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AFE4400: AFE4400 ADC saturation

anish singh1
Prodigy 180 points
Part Number: AFE4400

We are performing calibration of our custom afe4400 board using "ProSim SPOT Light SpO2 Pulse Oximeter Analyzer".

The afe4400 register configuration is same as of afe4400spo2_evm. Using this same configuration(Led1,2 = 4mA), the signal strength shown on  ProSim is around 30%.

So to improve signal strength(60-70%) we increased the LED1,2 current from 4mA to 10mA . Due to this, RED and IR adc data is saturated.

How to prevent adc saturation while maintaining good signal strength?

  • 0
    TI__Genius 12575 points

    Hi Anish,

    To get the better signal you have to control, LED current, Ambient DAC and TIA Gain.

    Typically the PPG signal will have following components,

    Iamb + Iled_dc + Iled_ac

    To avoid saturation you have to lower following components.

    Iamb :  This is due to ambient light and can be removed using Ambient DAC.

    Iled_dc :  This is due to LED's light reflected from skin and can be lowered using LED current.

    Once above two components (Iamb and  Iled_dc)  are lowered, you can apply higher TIA Gain to amplify the  Iled_ac  to get the stronger PPG signal.

    Regards,

    Prabin