Instructions
This tool shows ideal conversion behavior for the Analog Devices AD7732/34/38/39 Sigma-Delta ADCs. The goal is to illustrate how a digital Output Code is derived from VIN plus the Gain and Offset registers.
Select the desired part from the pulldown menu at the upper left of the schematic diagram. Then select the desired operating range (RNG bits) and conversion word-length in the fields at top of the gray form. Ordinarily, the input reference voltage should be kept at 2.5V.
Enter a voltage to be converted in the VIN field. The Output Code appears to the immediate right along with a sign bit.
When any of the output code fields or the over-range bit field is changed, the VIN value and sign-bit are recalculated.
When any other field is changed (including VIN), the output code fields and the over-range bit field are recalculated.
Conversion accuracy degrades in over-range mode and this tool may not reflect actual output code. Please check the datasheet for exact guarantees on over-range performance.
Over-range capability and per-channel offset and gain registers, as implemented above, are only available on the AD7732/34/38/39. However most other sigma-delta ADCs do contain offset and gain registers of one form or another. If the per-channel offset and gain registers are ignored and clamp is turned on then this should be a useful tool to predict approximate output code to input voltage relationship for any ADC technology.
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