This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AFE5809EVM: AFE5809EVM A/D conversion

Part Number: AFE5809EVM
Other Parts Discussed in Thread: AFE5809

Hello,

I need some help regarding AFE5809EVM.

First, we used internal test pattern generation to generate Ramp signal and then we decoded the lvds output. Figure 1. is the output for Ramp test pattern.  Note: We are using onboard clock which is 40MHz. Demodulator is bypassed.

Now, we selected test pattern to None and then feed the live signal which is Sine wave of 1MHz from a generator. everything is same no change. Here is the output we got:

From image we can see the our data is saturating. We are using 300mVpp input signal amplitude. which is acceptable range of afe input signal amplitude.

My questions:

1. Can you please suggest us, how we can get eliminate the saturation? so we can see the clear sine wave?

2. we want to use 400KHz to 500KHz signal, do we have to change any input capacitors for that frequency?

If you have any questions please just ask! Appreciate your help!

Thank you.

  • Hi Vatsal,

    The AFE5809 has an LNA gain of 18dB and a PGA gain of 24dB by default at startup as shown below.

    Without activating the attenuator, that means any signal you apply is automatically amplified by 42dB (~100X) in voltage. You can try a 1mV input signal or use the attenuator to prevent saturation.

    Sincerely,

    Olu

  • Hi Olu,

    Thanks for your reply. The problem I am facing is when I use attenuator or low voltage signal, my noise floor also increase and It distorted my signal.

    1. What is the maximum input voltage range AFE5809EVM can handle without any saturation or without use of the attenuator?

    Regards,
    Vatsal
  • Hi Vatsal,

    Without the attenuator (up to -40dB or 1/100 factor), leaving the LNA gain at 18dB, I was able to get a 5mV signal captured with no saturation/clipping.

    If you drop the LNA gain to 12dB, that raised it to ~10mV input voltage. These measurements are without a band-pass filter on the input.

    Also don't forget to click "En Digital TGC Attenuator" in the AFE5809GUI when using the attenuator (it shouldn't have a dramatic effect on your noise floor).

    Sincerely,

    Olu

  • Hi Olu,
    Thanks for your reply, Now I got the signal within the range. I've a question regarding Demodulator block.

    I'm bypassing DC removal, I want to generate I/Q signal and want to set downconversion frequency to 300KHz so my I can shift my baseband signal to ~150KHz. also, So I can use decimation of 32 which will give me sampling rate of 1.25MHz.

    1. How can I set LPF in decimation with cut-off frequency of 350KHz?
    2. I can create filter in MATLAB and create 112bit coefficient which can be load into coefficient RAM, for that What should I load into Profile RAM?

    Can you please help me with that?

    Thank you.