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Original question:

AFE5828: LVCMOS 1V8 input question2

AFE5828: CW and ATGC questions

BX27
Genius 3870 points
Part Number: AFE5828
Other Parts Discussed in Thread: AFE5808A, AFE58JD28, AFE5818

Hi, we are designing multiple AFE5828 on one board. some questions to consult.

1. Ti's EVM board sch snapshot shown as below. 

for pic 1, what's the purpose of resistor R44/R46 and R147(in pic2) ,  all 0 ohm, but DNP ?

fo pic2, I think the multiple AFE's CW output (CW_IP/QP_OUTP/M), should be simply summed through RC, then output toJ52/54, and then conditioned and ADC sampled. So, is the U16/U17 (as red circle marked) just for EVM board testing?

2. We noticed ATGC input range(-0.4~+0.4V) is very different from AFE5808A (we used before, 0~1.5V). so we revise the signal conditioning circuits as below PIC, RANGING -0.5V~+0.5V. could you please help review ? thanks !

By the way, is the differential cap C2177 across the final TGC ouput (TGC_CtrlP/N nets) necessary?

Thanks very much !

  • +1
    TI__Expert 4661 points

    Hi,

    Please find my response as below:

    1. AFE58JD28 CW output support Voltage and current output both. When device will be configured in current mode, we have to place 0 ohms in place of parts marked as DNP. In default voltage output mode, these components need not to be installed.

    2. Yes better to have differential cap to filter the noise coming from external TGC circuit.

    Thanks!

    Regards,

    Shabbir

  • +1 in reply to Shabbir Amjhera Wala
    Genius 3870 points

    Hi Shabbir, thanks for answering.

    1. So, for voltage mode, we just need to refer following pic which I grab from AFE5808A fig87, because I found no similar picture in AFE5828 datasheet about voltage mode, however there is only on picture about current mode (AFE5828 fogure 71). 

    And the EVM's sch , U16/U17 (as red circle marked) is  just for EVM board testing? 

    2.So , both of the singled-ended filtering caps and the differential cap are need.

    Please tell us if there is nay error in the ATGC signal conditioning circuit. thanks!

  • +1 in reply to BX27
    TI__Expert 4661 points

    Hi,

    1. Yes this figure looks correct for voltage mode output. In EVM U16, U17 is for testing.

    FYI, below is reference design for CW summing circuit

    https://www.ti.com/tool/TIDA-01351

    2. Yes cap is essential for both single ended and differential input mode. Functionality wise it looks fine but I am not sure about noise performance of your circuit. For your reference, below is app not for TGC control circuit. It is for AFE5818 but equally applicable for AFE5828. You have to change the common mode voltage only.

    https://www.ti.com/lit/an/slyt721/slyt721.pdf

    Thanks!

    Regards,

    Shabbir