ATtiny25 Automotive Atmel Corporation, ATtiny25 Automotive Datasheet - Page 123

• Manufacturer Part Number: ATtiny25 Automotive
• Manufacturer: Atmel Corporation

Specifications of ATtiny25 Automotive

• Flash (kbytes): 2 Kbytes
• Pin Count: 8
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 4
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 6
• Ext Interrupts: 6
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 4
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.12
• Eeprom (bytes): 128
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 125
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 5
• Pwm Channels: 6
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

18.7.5
7598H–AVR–07/09
ADC Multiplexer Selection Register – ADMUX
The values described in Table 51 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 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 sofware calibration can
be done utilizing the formula:
where V
is the temperature sensor offset value determined and stored into EEPROM as a part of produc-
tion test.
• Bit 7..6,4 – REFS2..REFS0: Voltage Reference Selection Bits
These bits select the voltage reference (V
are changed during a conversion, the change will not go in effect until this conversion is
complete (ADIF in ADCSR is set). Whenever these bits are changed, the next conversion will
take 25 ADC clock cycles. If active channels are used, using V
than (V
Table 18-3.
1.
• Bit 5 – ADLAR: ADC Left Adjust Result
The ADLAR bit affects the presentation of the ADC conversion result in the ADC Data Register.
Write one to ADLAR to left adjust the result. Otherwise, the result is right adjusted. Changing the
ADLAR bit will affect the ADC Data Register immediately, regardless of any ongoing conver-
sions. For a comple te description of this bit, see
on page
Temperature
Bit
Read/Write
Initial Value
REFS2
0
0
0
0
1
1
CC
TEMP
The device requires a supply voltage of 3V in order to generate 2.56V reference voltage.
126.
- 1V) as a voltage reference is not recommended, as this will affect the ADC accuracy.
is the ADC reading of the temperature sensor signal, k is a fixed coefficient and T
REFS1
=
Voltage Reference Selections for ADC
REFS1
0
0
1
1
1
1
k
R
7
0
V
TEMP
REFS0
REFS0
R/W
6
0
0
1
0
1
0
1
+
T
OS
ADLAR
R/W
Voltage Reference (V
V
External Voltage Reference at PB0 (AREF) pin, Internal Voltage
Reference turned off.
Internal 1.1V Voltage Reference without external bypass capacitor,
disconnected from PB0 (AREF).
Internal 1.1V Voltage Reference with external bypass capacitor at
PB0 (AREF) pin.
Internal 2.56V Voltage Reference without external bypass
capacitor, disconnected from PB0 (AREF).
Internal 2.56V Voltage Reference with external bypass capacitor at
PB0 (AREF) pin.
5
0
CC
used as Voltage Reference, disconnected from PB0 (AREF).
REF
REFS2
R
4
0
) for the ADC, as shown in
(1)
“The ADC Data Register – ADCL and ADCH”
MUX3
R
3
0
REF
) Selection
MUX2
R
2
0
CC
ATtiny25/45/85
or an external AREF higher
MUX1
R/W
1
0
Table
(1)
18-3. If these bits
MUX0
R/W
0
0
ADMUX
123
OS