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
69
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
System Resets, Interrupts, and Operating Modes, System Control Module
(SYS)
Table 1-7. ADC Calibration Tags
ADC
Calibration
TAG
ADC10: 13h
ADC12: 11h
Length
10h
Low Byte
CAL_ADC_GAIN_FACTOR
High Byte
Low Byte
CAL_ADC_OFFSET
High Byte
Low Byte
CAL_ADC_12T30
High Byte
Low Byte
CAL_ADC_12T85
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 at room temperature 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 ADC at room temperature with an external reference voltage of 2.5 V 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 (1.2 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)
The temperature coefficient, TC
SENSOR
in mV/°C, represents the slope of the equation. V
SENSOR
, in mV,
represents the y-intercept of the equation. Temp, in °C, is the temperature of interest.