CHAPTER 15:12-/10-/8-bit Analog to Digital Converter
S6J3200 Series Hardware Manual Document Number: 002-04852 Rev. *G
275
3.8.
A/D Converter Calibration
Additional feature of multiple conversion logical channels is selection of A/D Converter reference voltages
AVRH or AVRL for conversion instead of dedicated analog input signals. If AVRL conversion is wanted it
is enough to set one of ADC12Bn_MCCTRL0 to 3.AVRLSEL bits to "1" and trigger corresponding channel.
For AVRH conversion it is needed to set one of ADC12Bn_MCCTRL0 to 3.AVRHSEL bits to "1", set
corresponding ADC12Bn_MCCTRL0 to 3.AVRLSEL bit to "0" and trigger the dedicated channel.
If AVRHSEL or ARVRLSEL bits is set to "1", during the conversion of the corresponding channel mapping
of the logical channel to an analog inputs is disabled.
Figure 3-12 Example of Converted Digital Value Dependence on Input Voltage Level
This feature can be used to perform A/D Converter calibration. As it is shown on Figure 3-12 ideal
characteristics of A/D Converter would have:
−
transition between digital values 0x000 and 0x001 at AVRL + 0.5LSB input voltage level and
−
transition between digital values 0xFFEh and 0xFFF at AVRH - 1.5LSB input voltage level.
If this is not the case, A/D Converter can be calibrated by performing following steps:
−
Set gain correction setting (ADC12Bn_GCV.GCV) to "0".
−
Set a multiple conversion channel to highest priority and its AVRLSEL bit to "1".
−
For different ADC12Bn_OCV.OCV settings trigger the multiple conversion channel, i.e. perform
AVRL voltage conversion. It is better to configure multiple conversions of AVRL and calculate
average result (accumulated result divided by the number of executed conversions).
−
Find ADC12Bn_OCV.OCV setting x for which the transition between digital values 0x000 and 0x001
occurs.
−
Set AVRLSEL bit back to "0".
−
Set AVRHSEL bit to "1".
−
For different ADC12Bn_OCV.OCV settings trigger the multiple conversion channel, i.e. perform
AVRH voltage conversion. It is better to configure multiple conversions of AVRH and calculate
average result.
Ideal line
0x000
0x001
0x400
0x800
0xC00
0xFFF
AVRL
AVRH
Input voltage level
Converted digital binary value
Converted
values
Содержание S6J3200 Series
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