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AFE4300 : inconsistent IQ mode.

Esther Lee
Prodigy 50 points
Other Parts Discussed in Thread: AFE4300

Hello,

I have a problem about my board and code. I want to receive I and Q value in I/Q mode from AFE4300.

I also did check and set the IQ_MODE_ENABLE register, DEVICE_CONTROL2 register,  BCM_DAC_FREQ register and ADC_CONTROL_REGISTER2 register. 

Using the reference register which is 703 ohm, I received Q value higher than 3.0 at 16, 32 and 64 khz. However, sometimes it is less than 3.0..

I think its value shold be less than 3.0. (Because that value was less than 3.0 in GUI) But my value is not...What is the problem? any idea?

Thank you,

  • 0
    TI__Mastermind 49916 points
    Hello Esther,

    First thing to check is whether the excitation waveforms are getting generated properly. This is a common problem that is caused due to high electrode-skin contact impedance especially while using small form factor electrodes. If the excitation electrodes are connected to say, IOUT0 and IOUT1, then one of these pins should show a nice clean sine wave (around a DC of 0.9V) and the other should be close to a DC level of close to 0.9V. If these waveforms are not proper (for example, distorted), then it could be indicative of high skin-electrode contact impedances. These impedances come in series with the body impedance in the excitation path and can cause the excitation amplifier to saturate. That could result in unexpected results.