ATmega168A Atmel Corporation, ATmega168A Datasheet - Page 263

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ATmega168A

Manufacturer Part Number
ATmega168A
Description
Manufacturer
Atmel Corporation
Datasheets

Specifications of ATmega168A

Flash (kbytes)
16 Kbytes
Pin Count
32
Max. Operating Frequency
20 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
23
Ext Interrupts
24
Usb Speed
No
Usb Interface
No
Spi
2
Twi (i2c)
1
Uart
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
8
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
Yes
Crypto Engine
No
Sram (kbytes)
1
Eeprom (bytes)
512
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
3
Output Compare Channels
6
Input Capture Channels
1
Pwm Channels
6
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes

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24.7
24.8
8271D–AVR–05/11
ADC Conversion Result
Temperature Measurement
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
Table 24-3 on page 264
0x3FF represents the selected reference voltage minus one LSB.
The temperature measurement is based on an on-chip temperature sensor that is coupled to a
single ended ADC8 channel. Selecting the ADC8 channel by writing the MUX3...0 bits in
ADMUX register to "1000" enables the temperature sensor. The internal 1.1V voltage reference
must also be selected for the ADC voltage reference source in the temperature sensor measure-
ment. When the temperature sensor is enabled, the ADC converter 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
The voltage sensitivity is approximately 1 mV/°C and the accuracy of the temperature measure-
ment is +/- 10°C.
Table 24-2.
The values described in
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 application soft-
ware. The software calibration requires that a calibration value is measured and stored in a
register or EEPROM for each chip, as a part of the production test. The software calibration can
be done utilizing the formula:
T = { [(ADCH << 8) | ADCL] - T
where ADCn are the ADC data registers, k is a fixed coefficient and T
sor offset value determined and stored into EEPROM as a part of the production test.
Temperature / °C
Voltage / mV
IN
is the voltage on the selected input pin and V
Temperature vs. Sensor Output Voltage (Typical Case)
ATmega48A/PA/88A/PA/168A/PA/328/P
Table 24-2
and
Table 24-4 on page
OS
242mV
} / k
-45°C
are typical values. However, due to the process variation the
ADC
=
V
--------------------------
IN
V
REF
1024
265). 0x000 represents analog ground, and
REF
314mV
+25°C
the selected voltage reference (see
OS
is the temperature sen-
380mV
+85°C
Table
24-2.
263

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