TMS570 ADC Calibration

Hello Charles,

See answers to your questions below.

1) The TRM (SPNU99a) mentions two ADC offset calibration methods.  One method uses two points around the mid-point, the other uses those two plus the end-points.  What are the advantages / disadvantages of both methods?

Offset calibration is best done using the two mid-points. The zero-scale and full-scale conversions may be influenced by the amount of noise in the ground and reference supplies respectively.

2) There is no mention of gain calibration.  Is there a reason that gain calibration is not required, or would accuracy be improved by adding a manual gain cal?

You can calculate the gain error based on conversions using two reference voltages. The hardware does not support a mechanism to automatically correct for any gain error that your software algorithm calculates. This correction would have to be done manually on every read of the conversion results, if required.

3) Section 19.8.1 of the TRM says "This calibration sequence includes the conversion of an embedded calibration reference voltage followed by the calculation of an offset error correction value."  Is this embedded calibration reference different from the externally supplied VREFHI?

The internal reference voltages are generated using the VREFHI supply itself. Note that this calibration method only accounts for the ADC core's internal errors. Any error introduced by the circuitry between the supply source and the device terminals is not measured.

Regards,

Sunil