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AFE4490: SpO2 Calibration

Part Number: AFE4490
Other Parts Discussed in Thread: AFE4403

I been doing data conversion with the goal of SpO2 from the link provided below:

My values have been varying depending on the gains of both the infrared and red LEDs. I have tried the calibration methods of the document but haven't been successful. My question is if the device (AFE4490) needs to be calibrated through a different means other than adjusting the current and TIA gain, and calibrated against something such as a reference pulse oximeter. For that matter, if anyone has specific methods that have been using that would be very appreciated.

  • I am rather new to this field and would appreciate any feedback. I am currently getting SpO2 ranges of 95 +- 2. I am using a separate oximeter that is giving values of 98/99. The only thing I have obtained is that increasing the the TIA gain of the IR LED while decreasing the RED LED gives me higher and higher SpO2 readings, sometimes pass 100.

  • Hi,

    Would you please describe a bit more about "I have tried the calibration methods of the document but haven't been successful."?


    We don't have any additional particular suggestion for calibration, and it requires algorithms developed by customers.

    Something people could try might be that if people have have some "known true data/value" and some "non-calibrated data/values", then people can start building some regression or correlation equations, models, linear, or non-linear equations to find some coefficients, offsets, weighting factors, etc to approximately map the "non-calibrated data/values" to "known true data/value" for calibrations.



  • This would pertain to "How to Design Peripheral Oxygen Saturation (SpO2) and Optical Heart Rate Monitoring (OHRM) Systems Using the AFE4403" with using gains and current for certain ranges of the ADC Scale.

    I'm mainly wondering if TI had any standard tables that was empirically obtained from testing the AFE4490. If not, then would it be safe to assume the standard is 110 - 25*R? With regards to the second thing you said, I will try that, thank you!

  • Would you be a bit more specific on "any standard tables that was empirically obtained from testing the AFE4490"?

    Most characteristics tables and charts are already listed in the datasheet.


    Regarding to the equations model, "This model is often used in the literature in the context of medical devices.", which is also part of the algorithms development. And, it's customers decision to use it or not or develop something else.


    This document does not go into the details of the SpO2 calculation, instead, it discusses the key considerations on how to obtain a good quality PPG signal. The PPG signal can also be used to extract the heart rate information. Advanced applications with the PPG signal include vascular age, arterial stiffness index, and so forth. Irrespective of the target application, understanding the characteristics of light traveling through human body tissue is very important before one designs an LED lighting and photo detector module fitting into a given space and location. With mobile phones or wearable applications, there are also special constraints in space.



  • I would be referring to if the data sheet or anything had something like an SpO2 to ratio calibration curve for the AFE4490.

  • Hi,

    the real/true SpO2 value and the associated SpO2 calibration involves with different LEDs-PDs modules, optics, mechanical designs and algorithms, etc beforehand and is really towards to building a product. We don't have the expertise for those.