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DDC112: Reason for offset between Integrators

Christof
Prodigy 100 points
Part Number: DDC112

Dear Forum,
I am using a DDC112 to measure the current flowing through a fixed resistor. The source voltage (0.5V) and resistor (201k Ohm) are very stable and precise.
I have tested many resistors (up to 1GOhm ) and have always the same strange issue with the measured values.

The values from the same integrator are almost identical to each other, but the difference between the integrators is about 5% (this happens with internal and external capacitors alike). This is the same with channel 1 and 2. In test mode, I observe the mentioned 0.2pC difference, and all seems fine.

What can cause this issue?

Best regards
Christof

  • 0
    TI__Mastermind 49206 points

    Hi Christof,

    Based on your voltage source of 0.5V and resistors between 201k to 1GOhm, you are feeding in a current of 0.5nA to 2.4uA. Is that correct?

    What is your integration time (Tint)?

    If I understand your question correctly, irrespective of the input range selected, your output code mismatch across channels is about 5% always. Is it 5% of FSR?

    This is also true across side A and side B. Is that correct?

    Can you please share your experiment data?

  • 0 in reply to Praveen Aroul
    TI__Mastermind 49206 points

    Hi Christof,

    Since I did not hear back from you, I believe you were able to resolve the issue.

    I will close the post and if you have any pending questions, feel free to post them here.