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SENSOR
SENSOR
SENSE
V
Temp
TC
V
+
´
=
15
2
1
_
_
_
)
(
)
_
(
´
´
=
FACTOR
GAIN
ADC
CAL
raw
ADC
corrected
gain
ADC
OFFSET
ADC
CAL
corrected
gain
ADC
final
ADC
_
_
)
_
(
)
(
+
=
15
2
1
_
_
_
)
(
)
_
(
´
´
=
FACTOR
GAIN
ADC
CAL
raw
ADC
corrected
gain
ADC
15
2
1
_
_
_
´
=
GAIN
FACTOR
GAIN
ADC
CAL
OFFSET
ADC
CAL
raw
ADC
corrected
offset
ADC
_
_
)
(
)
_
(
+
=
Device Descriptor Table
1.14.3.2 ADC Offset and Gain Calibration
shows the ADC calibration tags.
Table 1-7. ADC Calibration Tags
ADC
TAG
ADC10: 13h
Calibration
ADC12: 11h
Length
10h
Low Byte
CAL_ADC_GAIN_FACTOR
High Byte
Low Byte
CAL_ADC_OFFSET
High Byte
Low Byte
CAL_ADC_15T30
High Byte
Low Byte
CAL_ADC_15T85
High Byte
Low Byte
CAL_ADC_20T30
High Byte
Low Byte
CAL_ADC_20T85
High Byte
Low Byte
CAL_ADC_25T30
High Byte
Low Byte
CAL_ADC_25T85
High Byte
The offset of the ADC is determined and stored as a twos-complement number in the TLV structure. The
offset error correction is done by adding the CAL_ADC_OFFSET to the conversion result.
(4)
The gain of the ADC12 is calculated by
:
(5)
The conversion result is gain corrected by multiplying it with the CAL_ADC_GAIN_FACTOR and dividing
the result by 2
15
:
(6)
If both gain and offset are corrected, the gain correction is done first:
(7)
1.14.3.3 Temperature Sensor Calibration
The temperature sensor calibration data is part of the ADC tag as shown in
.
The temperature sensor is calibrated using the internal voltage references. Each reference voltage (1.5 V,
2.0 V, or 2.5 V) contains a measured value for two temperatures (30°C ± 3°C and 85°C ± 3°C) and are
stored in the TLV structure. The characteristic equation of the temperature sensor voltage, in millivolts is:
(8)
47
SLAU272C – May 2011 – Revised November 2013
System Resets, Interrupts, and Operating Modes, System Control Module
(SYS)
Copyright © 2011–2013, Texas Instruments Incorporated