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ADS9224R: Data acquisition issue after power-up

Part Number: ADS9224R

Hi, 
Customers are evaluating the ADS9224R.
However, it is a conversion result with a small amplitude from immediately after the power is turned on to about 1500 sampling.

Before the ADC started sampling, it was confirmed that the correct sine wave was input to the differential input PIN.

I described the circuit configuration in the material.
Can the TI team give me any advice?



ADS9224R.pptx

Best regards,

Hiroshi

  • Hello Hiroshi-san,

    Thank you for your post and for providing such great detail.

    You could try increasing the input capacitors by 10x on the differential and common-mode caps, but I do not see how this would produce the issue described in the PPT. 

    Could you capture a scope image of the internal reference voltage (REFOUT) and the reference buffer outputs (REFP_A and REFP_B) during power up (slide 9) and also during the HW reset tests (slide 11)? 

    Regards,

    Ryan

  • Hi Ryan-san,

    Thank you for your reply.
    I ask the customer to confirm the REFOUT,REFP/B.

    Best regards,

    Hiroshi

  • Hi Ryan-san,

    This is a customer comment.
    "REFOUT is stable at the voltage stated in the data sheet. REFP_A / B and REFby2 are also stable."

    I'm looking at the UG for DS and EVM, but I can't find any problems.
    Do you have any advice?

    Ask if the customer can evaluate with EVM to see if the customer's measurement system is right.

    Best regards,
    Hiroshi

  • Hello Hiroshi-san,

    If the customer has an EVM to evaluate, I think that would be a good comparison. However, they will not have the same timing control with respect to power-on. In the PPT, the customer noted that they wait 150 ms after power supplies are stable to write to the device registers and collect data. However, my understanding is that the customer does not believe this problem is related to power-on timing, correct? Only the first ~1500 samples show this issue.

    Two recommendations I would suggest trying on the amplifier circuit:

    1. Increase the charge-bucket capacitors 10x
    2. Short the two input 1-uF caps

    Best regards,

    Ryan

  • Hi Ryan-san,

    Our customer will retest based on your advice. It will take some time to get the parts, but we will report the test results in this thread.

    Best regards,
    Hiroshi