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DDC264 Offset between side-A and side-B

higa daisuke
Intellectual 900 points
Other Parts Discussed in Thread: DDC264, OPA365, REF3040

Hi support team

My customer is evaluating X-RAY baggage inspection system using DDC264 customed board.

They found offset (at output code) between side-A and side-B on same input channel.
It is 67LSB on the average of 50 data.( Please reffer to the attached exel file.)

I received inquiries about the cause of offset from them.

I think that one of factor is offset channel mismach(+-150ppm(tpy)).

Can you advise about other factor.?

Customer configuration detail

Output mode : 16bit mode
Gain setting : gain0(12.5pC)
Integration time : 800us
Csensor : approximately 60pF
FSR : 4.096V
Signal path : PD -> DDC264
REF circuit : DC5V -> REF3040 -> OPA365 -> DDC264

Other information
Application : X-RAY baggage inspection system

Best regardsOffset between sideA and sideB.xlsx

  • 0
    TI__Guru 63160 points

    Hello,

    You are correct, this mismatch is normal and is within the Offset Mismatch spec you mentioned.

    The reason for this mismatch is because the A-Side and B-Side integration capacitors are seperate and have slight differences depending on the silicon manufacturing process. These values are trimmed during production but they cannot be exactly matched.

    Regards,

    -Adam