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AFE5818EVM: AFE5818 collects DC voltage or low frequency square wave signal

Zhonghui Xu
Expert 5445 points
Part Number: AFE5818EVM
Other Parts Discussed in Thread: AFE5818,

Hi team,

How does the AFE5818 evaluation board collect DC voltage or collect low-frequency square wave signals around 10KHz? Is it possible to change the capacitance of the input to 0 ohmic resistance?

Thank you very much for your help.

Best regards,

  • 0
    TI__Genius 12025 points

    Hi,

    Thanks for using the AFE5818 device.

    From the AFE5818EVM board and Datasheet as the customer can see,

    this is designed using AC input signal with using input capacitor at INMx input pin.

    You can change this cap value by referring to the datasheet Table 1 page 36

    and change Cbypass value as you require for your input signal frequency value.

    However, please don't change the capacitor to be a resistor.

    Thank you!

  • 0 in reply to Chen Kung
    TI__Expert 5445 points

    Hi Kung,

    Thank you for your help.

    There are still some questions to ask.

    1. Why can't the capacitor be replaced with a resistor? What is the impact of replacing it with a resistor?

    2. If a 2.2V bias voltage is applied to the input signal after changing the resistance, can the 2.2V bias voltage input at the negative end be offset at the LNA end?

    Thanks a lot.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 5445 points

    Hi Kung,

    Thank you for your help.

    Is there any update?

    Thanks a lot.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Genius 12025 points

    Hi,

    Thanks for using AFE5818EVM and device.

    Please take a look at the AFE5818 datasheet page 14,

    it shows the Input common mode voltage at INP and INM pins

    is 2.2V typical value which can change from chip to chip.

    Also if the customer wants to run the input signal with very low frequency,

    they can look at the datasheet page 36 Table 1

    you can see how to calculate the HPF corner freq by using different Cbypass value

    by the customer (externally, not inside the device).

    Thank you!

  • 0 in reply to Chen Kung
    TI__Expert 5445 points

    Hi Kung,

    Thank you for your help.

    Best regards,