Adc Special Modes - Texas Instruments TMS570LC4357 Technical Reference Manual

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22.2.6 ADC Special Modes

The ADC module supports some special modes for diagnostics and power saving purposes.
22.2.6.1 ADC Error Calibration Mode
The application program can activate a calibration sequence any time self-test mode is disabled
(SELF_TEST = 0). This calibration sequence includes the conversion of an embedded calibration
reference voltage followed by the calculation of an offset error correction value.
NOTE: Disable Self-Test Mode Before Calibration
To avoid errors during the calibration operation, self-test mode must not be enabled during a
calibration sequence. In addition, to ensure accurate results, calibrate the ADC in an
environment with minimum noise.
Calibration mode is enabled by setting the CAL_EN bit (ADCALCR.0). The application needs to ensure
that no conversion group is being serviced when the calibration mode is enabled.
The input multiplexor gets disabled and only the reference voltage is connected to the ADC core input.
Switch S5 of Figure 22-13
the ADC core to the calibration and offset error correction register, ADCALR. The ADC results' memory is
not affected by the calibration conversion.
When calibration mode is disabled, the ADC can be configured for normal conversions.
AD
REFHI
AD
REFLO
ADIN0
ADIN31
22.2.6.1.1 Calibration Conversion
The calibration conversion also needs to meet the minimum sampling time specification for the ADC. This
value is typically 1 us. The Event Group sample time register (ADEVSAMP) is used to specify the number
of ADCLK cycles for the calibration conversion.
The BRIDGE_EN and HILO bits (ADCALCR.9:8) control the voltage to the calibration reference device
shown in Figure 22-15. The positions of the switches in calibration mode are listed in
SPNU563A – March 2018
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is opened. In addition, the digital result issued from a conversion is output from
Figure 22-13. Self-Test and Calibration Logic
Self-test and
R1 ~ 5K
R2 ~ 7K
S1 S2
MUX
V
S5
in
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calibration
S3 S4
R1
R2
ADC Core
ADCALR.9:0
ADDRx.16,9:0
Analog To Digital Converter (ADC) Module
Basic Operation
CALR
Table 22-2.
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