Datasheet

30+
T30CAL_ADC_25–T85CAL_ADC_25
30–85
×T30)CAL_ADC_25–(ADC(raw)=Temp
30+
T30CAL_ADC_15–T85CAL_ADC_15
30–85
×T30)CAL_ADC_15–(ADC(raw)=Temp
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24.2.2 TAG_ADC12_1 Calibration TLV Structure
The calibration data for the ADC12 module consists of eight words (see Table 24-4).
Table 24-4. TAG_ADC12_1 Calibration Data (Device Specific)
Label Description Offset
CAL_ADC_25T85 VREF2_5 = 1, T
A
= 85°C ± 2°C, 12-bit conversion result 0x0E
CAL_ADC_25T30 VREF2_5 = 1, T
A
= 30°C ± 2°C, 12-bit conversion result 0x0C
CAL_ADC_25VREF_FACTOR VREF2_5 = 1, T
A
= 30°C ± 2°C 0x0A
CAL_ADC_15T85 VREF2_5 = 0, T
A
= 85°C ± 2°C, 12-bit conversion result 0x08
CAL_ADC_15T30 VREF2_5 = 0, T
A
= 30°C ± 2°C, 12-bit conversion result 0x06
CAL_ADC_15VREF_FACTOR VREF2_5 = 0, T
A
= 30°C ± 2°C 0x04
CAL_ADC_OFFSET VeREF = 2.5 V, T
A
= 85°C ± 2°C, f
ADC12CLK
= 5 MHz 0x02
CAL_ADC_GAIN_FACTOR VeREF = 2.5 V, T
A
= 85°C ± 2°C, f
ADC12CLK
= 5 MHz 0x00
24.2.2.1 Temperature Sensor Calibration Data
The temperature sensor is calibrated using the internal voltage references. Each reference voltage (1.5 V
and 2.5 V) contains a measured value for two temperatures, 30°C±2°C and 85°C±2°C and are stored in
the TLV structure at the respective SegmentA location (see Table 24-4). The characteristic equation of the
temperature sensor voltage, in mV, is:
V
SENSE
= TC
SENSOR
× Temp + V
SENSOR
(1)
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.
The temperature (Temp, °C) can be computed as follows for each of the reference voltages used in the
ADC measurement:
(2)
24.2.2.2 Integrated Voltage Reference Calibration Data
The reference voltages (VREF2_5 = 0 and 1) are measured at room temperature. The measured value is
normalized by 1.5 V or 2.5 V before stored into the flash information memory SegmentA.
CAL_ADC_15VREF_FACTOR = (Ve
REF
/ 1.5 V) × 2
15
The conversion result is corrected by multiplying it with the CAL_ADC_15VREF_FACTOR (or
CAL_ADC_25VREF_FACTOR) and dividing the result by 2
15
.
ADC(corrected) = ADC(raw) × CAL_ADC_15VREF_FACTOR × (1 / 2
15
)
24.2.2.3 Example Using the Reference Calibration
In the following example, the integrated 1.5-V reference voltage is used during a conversion.
• Conversion result: 0x0100
• Reference voltage calibration factor (CAL_ADC_15VREF_FACTOR): 0x7BBB
The following steps show an example of how the ADC12 conversion result can be corrected by using the
hardware multiplier:
1. Multiply the conversion result by 2 (this step simplifies the final division).
2. Multiply the result by CAL_ADC_15VREF_FACTOR.
3. Divide the result by 2
16
(use the upper word of the 32-bit multiplication result RESHI).
584
TLV Structure SLAU144J–December 2004–Revised July 2013
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