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DDC1128EVM: DDC1128EVM raw output code to current

Part Number: DDC1128EVM
Other Parts Discussed in Thread: DDC1128, , REF3040

Dear Sir/Madam,

Currently we are evaluating a DDC1128 Current-Input Analog-to-Digital Converter using the DDC1128EVM evaluation board. I would like to convert the raw output codes to a current in A (nA, uA, etc.). I can’t figure out how to calculate this.

This is how I tried to calculate it:

  1. Full-scale 100% is equal to 150pC according table 7 in the datasheet.
  2. 100% is equal to 0xFFFFF (decimal 1048575)
  3. 150pC / 1048575 = 0,000143051284 pC/step
  4. Capture data using the PC software, this gives me a raw value of e.g. decimal 4011
  5. 011 x 0,000143051284 = 0,57 pC while the PC software says -0,01220 pC. What am I doing wrong?

Does the Vref influence the value in Coulombs? I am using the onboard reference (REF3040, 4.096V).

Using the value in Coulombs and Tint (integration time), the current in Amps can be calculated.

So in short: What’s the equation for converting the raw values to amps?

Thank you very much in advance!