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AFE4404: Alternate use suitability

Joshua Gammie
Prodigy 10 points
Part Number: AFE4404

Hello there,

We're currently looking at using the AFE4404 to drive an LED for 5us and read back a different wavelength for 10us using a PD. We're specifically looking at the intensity and decay time of the PD reading. Is the AFE4404 and the AFE4404 EVM specifically configured for optical heart rate monitoring, or is there flexibility in its use?

Thanks

  • 0
    TI__Mastermind 49716 points

    Hello Joshua,

    I believe you are probably looking for an integrator to look at the PD current intensity drop. AFE4404 is designed to read out low bandwidth signal similar to heart rate signal.

    Also 5 us is too small led on time to drive an LED with AFE4404.

    What are PD current levels and SNR requirements for the application?

  • 0 in reply to Praveen Aroul
    Prodigy 10 points

    Hello Praveen,

    Thank you for getting back to me on this. We'll move down the route of a separate LED driver and OP amp as an integrator. 

    We're trying to get our system to be as low powered as possible, while fitting onto our device, with a maximum chip dimension of 4x4x1mm. We're most likely looking at around 0.8uA of current from the PD due to our low power requirements, so the lower the SNR the better. 

    Kind regards,

    Joshua

  • 0 in reply to Joshua Gammie
    TI__Mastermind 49716 points

    Hello Joshua,

    Thanks for your reply. Though the AFE can handle the PD currents, it may not be to handle the led on times. I will close the post.