Atmel ATmega32M1 User Manual (English)

To Next Page

To Previous Page

243

7647H–AVR–03/12

Atmel ATmega16/32/64/M1/C1

18.8 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 2.56V 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.

As shown Figure 18-14, the temperature sensor is followed by a driver. This driver is enabled

when ADMUX value selects the temperature sensor as ADC input See “ADC Input Channel

Selection” on page 246. The propagation delay of this driver is approximatively 2µS. Therefore

two successive conversions are required. The correct temperature measurement will be the sec-

ond one.

One can also reduce this timing to one conversion by setting the ADMUX during the previous

conversion. Indeed the ADMUX can be programmed to select the temperature sensor just after

the beginning of the previous conversion start event and then the driver will be enabled 2 µS

before sampling and hold phase of temperature sensor measurement. See “Changing Channel

or Reference Selection” on page 235.

Figure 18-14. Temperature Sensor Block Diagram

The measured voltage has a linear relationship to the temperature as described in Table 18-3 on

page 243. The voltage sensitivity is approximately 2.5 mV/

°C and the accuracy of the tempera-

ture measurement is +/- 10°C after bandgap calibration.

The values described in Table 18-3 on page 243 are typical values. However, due to the process

variation the temperature sensor output voltage varies from one chip to another. To be capable

of achieving more accurate results, the temperature measurement can be calibrated in the appli-

cation software.

Table 18-3. Temperature vs. Sensor Output Voltage (Typical Case)

Temperature / °C -40°C +25°C +125°C

Voltage / mV 600 mV 762 mv 1012 mV

Temperature

Sensor

ADC

Input

Multiplexer

ADMUX

to sampling

and hold

G=1

Enable when

ADMUX = Temp. Sensor input

Need help?

Do you have a question about the Atmel ATmega32M1 and is the answer not in the manual?

Atmel ATmega32M1 Specifications

General

Architecture	8-bit AVR
Flash Memory	32 KB
SRAM	2 KB
EEPROM	1 KB
Clock Speed	16 MHz
GPIO Pins	32
I/O Pins	32
ADC Channels	8
ADC Resolution	10-bit
UART	1
USART	1
SPI	1
I2C	1
PWM Channels	6
CAN	1
Operating Voltage	2.7V - 5.5V
Operating Temperature	-40°C to +85°C
Temperature Range	-40°C to +85°C
Package	44-TQFP, 44-QFN