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AC component of PPG signal from AFE4400 only 0.5mV and DC bias is about 0.7V, why?how can I raise the AC signal amplitude?

Other Parts Discussed in Thread: AFE4400

HI

  I am using AFE4400 to  sample the PPG signal, some parameter of  registers setting as following:

But the signal I get from AFE4400 shown as following:

PRF=125HZ

LED is SFH7050, and I only use the RED and IR in our system

  • Liang,

    There are a few knobs you can turn to increase the signal. I would try increasing your LED current first to see if you can get at least 1mV pk-pk.

  • Hi Amy Schnoor

    thank you very much for your reply,

    I have a test with your advise, I found that in my solution if I increase the current of LED, the signal of RED and IR signal is very bad, The default value of LEDCNTRL register is 0x011414ul, so the phenomenon is as shown below if I increase the value to such as 0x011515ul,and the DC component is larger than before default setting。

    now in my system the first TIA amplifier RF is 100K and the second amplifier is 0Db gain.my question is why the DC component is so large the the AC component is so small? can you explain to me why?

    thank you

  • Liang,

    If you have high ambient light, your DC value could be very large. What's the setting you are testing under? Have your tried using our EVM?