Datasheet

254
7810C–AVR–10/12
Atmel ATmega328P [Preliminary]
23.7 ADC Conversion Result
After the conversion is complete (ADIF is high), the conversion result can be found in the ADC
Result Registers (ADCL, ADCH).
For single ended conversion, the result is
where V
IN
is the voltage on the selected input pin and V
REF
the selected voltage reference (see
Table 23-3 on page 256 and Table 23-4 on page 257). 0x000 represents analog ground, and
0x3FF represents the selected reference voltage minus one LSB.
23.8 Temperature Measurement
The temperature measurement is based on an on-chip temperature sensor that is coupled to a
single ended ADC input. MUX[4..0] bits in ADMUX register enables the temperature sensor. The
internal 1.1V voltage reference must also be selected for the ADC voltage reference source in
the temperature sensor measurement. When the temperature sensor is enabled, the ADC con-
verter can be used in single conversion mode to measure the voltage over the temperature
sensor.
The measured voltage has a linear relationship to the temperature as described in Table 23-2 on
page 254.
The voltage sensitivity is approximately 1LSB/
°C and the accuracy of the temperature measure-
ment is ±
10°C using manufacturing calibration values (TS_GAIN, TS_OFFSET).
The values described in Table 23-2 on page 254 are typical values. However, due to the process
variation the temperature sensor output varies from one chip to another.
23.8.1 Manufacturing Calibration
Calibration values determined during test are available in the signature row.
The temperature in degrees Celsius can be calculated using the formula:
ADC
V
IN
1024⋅
V
REF
--------------------------=
Table 23-2. Sensor output code vs Temperature (typical values)
Temperature / °C -40°C +25 °C +125 °C
0x010D
0x0160
0x01E0