The ADC12DLx500 has foreground calibration available. When foreground calibration is initiated the ADCs are automatically taken offline and the output data become mid-code (0x000 in 2's complement) while a calibration is occurring. Additional offset calibration features are available in foreground calibration mode. Further, a number of ADC parameters can be trimmed to optimize performance in a user system.

The ADC12DLx500 consists of a total of six sub-ADCs, each referred to as a bank, with two banks forming an ADC core. The banks sample out-of-phase so that each ADC core is two-way interleaved. The six banks form three ADC cores, referred to as ADC A, ADC B, and ADC C. In foreground calibration mode, ADC A samples INA± and ADC B samples INB± in dual-channel mode and both ADC A and ADC B sample INA± (or INB±) in single-channel mode.

Figure 6-4 shows a diagram of the calibration system including labeling of the banks that make up each ADC core. When calibration is performed, the linearity, gain, and offset voltage for each bank are calibrated to an internally generated calibration signal. The analog inputs can be driven during calibration except that when offset calibration (see CAL_OS in the CAL_CFG0 register) is used. There must be no signals (or aliased signals) near DC for proper estimation of the offset (see Section 6.4.8).

Figure 6-4 ADC12DLx500 Calibration System Block Diagram

In addition to calibration, a number of ADC parameters are user-controllable to provide trimming for optimal performance. These parameters include input offset voltage, ADC gain, interleaving timing, and input termination resistance. The default trim values are programmed at the factory to unique values for each device that are determined to be optimal at the test system operating conditions. The factory-programmed values can be read from the trim registers and adjusted as desired. The register fields that control the trimming are labeled according to the input that is being sampled (INA± or INB±), the bank that is being trimmed, or the ADC core that is being trimmed. Trim values are not expected to change as operating conditions change, however optimal performance can be obtained by doing so. Any custom trimming must be done on a per device basis because of process variations, meaning that there is no global optimal setting for all parts. See Section 6.4.9 for information about the available trim parameters and associated registers.