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AFE5851EVM More Detail

Jhin Ci Hong
Prodigy 250 points
Other Parts Discussed in Thread: AFE5851EVM, AFE5851

Hello,

We are using TSW1400EVM and AFE5851EVM to implement some system.

And to let the AFE input signal and output signal be more accurate, we want to know more about AFE5851EVM.

As we know, AFE5851EVM have anti-alias low-pass filter, high-pass filter, variable gain amplifier, ADC...etc.

Like this picture.  If you have time, can you explain more about this ? 

Or as we know, the data is simply transport as below way.

Analog input  => VGA => ADC

The analog input is limited 1Vpp, and ADC input is limited 2Vpp.

So I try two different signal input the AFE5851EVM, (-1Volt~0Volt sine wave, and 0Volt~+1Volt sine wave)

And I get same waveform in HSDC Pro.

Is it means the analog input data have been removed DC(offset)?(Which place to removed the DC)

After I try more tests for capturing in the HSDC Pro, all waveform are average in 204X point.

So I have two more questions.

Is 0~4095(12bits 00...00 ~ 11...11) point in HSDC Pro means the 2Vpp?

And all capture data would average to the middle point?

And I do one more test for analog input.

As we over the 1Vpp limit, the waveform we captured is like below.(input 1.8Vpp sine wave,0dB)

The waveform isn't over the 2Vpp, but is different to others.

Why the waveform (over 1Vpp) would be like below picture?

p.s. Because our data would in 100kHz. So all above i mentioned test is in DC coupling mode.

My email

JhinCiHong19901008HY@gmail.com

Kind regards,

Jerry

  • 0
    TI__Mastermind 18285 points
    Jerry,

    I've assigned your post to the correct apps engineer. He should respond soon.
  • 0
    TI__Genius 12025 points

    Hi Jhin,

    How are you?

    Yes, The analog input signal DC (offset) from the input connector is blocked by the serial 0.1uF cap

    on the AFE5851EVM.

    Therefore if your input signal is tied to GND (No AC input) then you can see the captured signal data should be close to middle code (2048).

    Yes, internal ADC 12bit output (0...4095) is related to the ADC input 2Vpp signal range.

    Yes, we also can see the same result as you shown when the input signal over 1Vpp.

    Because AFE5851 Data Sheet specs the input signal can only allow 1Vpp as Max value, if the input signal is running greater than 1Vpp, the signal will get distorted and out of the linear range. Therefore you could see the signal waveform is not linear anymore.

    If the larger signal can happen very often, please add clamp circuitry on your board to clip the huge signal amplitude off to avoid the unpredicted case suddenly happened.

    Thank you very much.

    Best regards,

    Chen