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AFE5801: SDOUT issue

Part Number: AFE5801
Other Parts Discussed in Thread: AFE5809

Hi

We are using three adc AFE5801 , and all SPI control is muxed with a single FPGA master control , SPI write is working fine 

But Read is not happening , SDOUT not giving any data , Is this because three devices are running on the same line ??

as per the datasheet pull up is not recommended only for SDOUT , so we have not added any pullup for this line .

But if we disconnect two devices and keep only one device , then SDOUT is fine 

we want SDOUT to work when all three devices are connected

  • Hi Akshay,
    How are you?
    Yes, you are right. AFE5801 is our earlier device which does not include SDOUT output pin
    with tri-state option. So either you need to use different pins on your FPGA to capture each SDOUT pin
    or you need to add one buffer externally for each SDOUT pin and enable or disable each buffer when you need.
    For newer device such as AFE5809 device on its Datasheet page 49,
    you can see it adds such new option to allow different SDOUT pins from different AFE devices
    can be linked together.

    Thank you!
    Have a nice day!

    Best regards.
    Chen
  • Hi Chen

    I have a TCXO oscillator which generates sine wave and this is buffered through an analog buffer PL133-37 and sent to all three afe5801 adc as single ended clock input with clkm grounded via 0.1uF cap , with this sine wave clock we see that ADC outputs is always zero , then we understood from datasheet that sine wave has to be sent via capacitor , we tried this by lifting buffer output pin and connecting a series capacitor from pin to pad so that clkp of afe5801 gets clock via capacitor since it is sine wave , what should be the capacitor value to be used to make sure adc always works , since adc expects clkp series capacitor very close to it but we are putting it at buffer output
  • Hi Akshay,

    Please look at and refer to the AFE5801 Users Guide:
    "Figure 14. Schematic Page 1"
    P3's 4-3 only
    P2's 4-3 only
    P4's 3-2
    P5's 3-2
    P6 is shorted.

    Hope this can help.

    Thank you!

    Best regards,
    Chen
  • Hi Akshay,

    How are you?

    Here is the schematic showing how we connect clock as single-ended input.

    Please take a look:

    Thank you!

    Best regards,

    Chen