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FDC2212: EVK test issue

Piero Yu
Intellectual 950 points
Part Number: FDC2212

1. The difference between the capacitance value measured by the online simulation and the data displayed by the waveform is relatively large. When the hand is placed on the board, the capacitance becomes smaller (the waveform display feels right and the test result seems to be problematic);
2. The software always displays the channel 0 unconverted error;
3,  EVK board（bought from Ti web） provided 18uH inductance is not welded, I do not know if this is intentional, parasitic inductance has 18uH or how to say

Pls kindly help

  • 0
    TI__Expert 6625 points
    Hi Piero,
    Can you provide more information about this online simulation? For your configuration, can you try differential measurement and let us know if that fixes your issue. Can you also provide a screenshot of the software error? The EVM board already comes with sensor coil with inductance of about 18uH (so no need to solder an inductor in place).

    Best Regards,
    Bala Ravi
  • 0 in reply to Bala Ravi
    Intellectual 950 points

    The online simulation diagram can be referred to the attachment.

    1. According to the normal situation, the capacitance values measured by channel 0 and channel 1 should be similar, because their disk size is around the same,  but the difference between the measured capacitance value is 2pF;

    2, channel 0 status showed a conversion error

  • 0 in reply to Piero Yu
    TI__Intellectual 1020 points
    Hi Pierro

    Thanks for your response. Our response may be delayed due to holiday season, we will get back to you as soon as possible.

    Regards,

    Vaibhav Garg
  • 0 in reply to Vaibhav Garg10
    TI__Expert 6625 points
    Hi Pierro,
    2pF difference in capacitance is normal. This is likely due to layout asymmetry and parasitic capacitance along the INA/INB traces. Even if the intended sensors are exactly the same size, the INA/INB traces are still part of the full sensor. The layout of nearby traces can also influence the parasitic capacitance. For your application, CH0 unread conversion is not an issue, all it means is that when trying to read converted data via I2C it failed. I think if you click on "Detect Idrive Init" button the NaN would disappear, also this is not an issue unless you're actively trying to use this function.

    Best Regards,
    Bala Ravi