ATmega328P datasheet(254/345 Pages) ATMEL

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254

7810A–AVR–11/09

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 VREF 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

VIN 1024

⋅

VREF

-----------------------------

Table 23-2.

Sensor output code vs Temperature (typical values)

Temperature / °C

-40°C

+25 °C

+125 °C

0x010D

0x0160

0x01E0

ATmega328P Datasheet(PDF) 254 Page - ATMEL Corporation

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