XC164-16 Datasheet, PDF (99/417 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC164-16 Derivatives
Peripheral Units (Vol. 2 of 2)
The Analog/Digital Converter
16.3
Automatic Calibration
The ADC of the XC164 features automatic self-calibration. This calibration corrects gain
errors, which are mainly due to process variation, and offset errors, which are mainly due
to temperature changes.
Two types of calibration are supported:
• Reset calibration performs a thorough basic calibration of the ADC after a reset. In
particular this is required after a power-on reset.
• Post-calibration performs one small calibration step after each conversion.
Reset Calibration
After a reset, a thorough power-up calibration is performed automatically to correct gain
and offset errors of the A/D converter. To achieve best calibration results, the reference
voltages as well as the supply voltages must be stable during the power-up calibration.
During the calibration sequence a series of calibration cycles is executed, where the step
width for adjustments is reduced gradually. The total number of executed calibration
cycles depends on the actual properties of the respective ADC module. The maximum
duration of the power-up calibration is 11,696 cycles of the basic clock f_BC.
Status flag CAL is set as long as this power-up calibration takes place.
Note: The reset calibration must be completed (CAL = 0) before entering Sleep mode,
Idle mode, or Powerdown mode. Otherwise, the analog comparator remains
active and draws its supply current, which is undesired during power-save
conditions.
Post-Calibration
After each conversion a small calibration step can be executed. For 8-bit and 10-bit
conversions post-calibration is not mandatory in order not to exceed the total unadjusted
error (TUE) specified in the data sheet. Post-calibration can be disabled by setting bit
CALOFF in register ADC_CTR0. When disabled, the post-calibration cycles are skipped
which reduces the total conversion time.
Note: Calibration may be disabled only after the reset calibration is complete.
User’s Manual
ADC_X41, V2.1
16-17
V2.1, 2004-03