ATtiny25 Automotive Atmel Corporation, ATtiny25 Automotive Datasheet - Page 112

• 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

18.2
112
Operation
ATtiny25/45/85
Figure 18-1. Analog to Digital Converter Block Schematic
The ADC converts an analog input voltage to a 10-bit digital value through successive approxi-
mation. The minimum value represents GND and the maximum value represents the voltage on
V
The voltage reference for the ADC may be selected by writing to the REFS2..0 bits in ADMUX.
The VCC supply, the AREF pin or an internal 1.1V / 2.56V voltage reference may be selected as
the ADC voltage reference. Optionally the internal 1.1V / 2.56V voltage reference may be decou-
pled by an external capacitor at the AREF pin to improve noise immunity.
The analog input channel and differential gain are selected by writing to the MUX3..0 bits in
ADMUX. Any of the four ADC input pins ADC3..0 can be selected as single ended inputs to the
ADC. ADC2 or ADC0 can be selected as positive input and ADC0, ADC1, ADC2 or ADC3 can
be selected as negative input to the differential gain amplifier.
If differential channels are selected, the differential gain stage amplifies the voltage difference
between the selected input pair by the selected gain factor, 1x or 20x, according to the setting of
the MUX3..0 bits in ADMUX. This amplified value then becomes the analog input to the ADC. If
single ended channels are used, the gain amplifier is bypassed altogether.
CC
, the voltage on the AREF pin or an internal 1.1V / 2.56V voltage reference.
ADC3
ADC2
ADC1
ADC0
AREF
V
CC
INTERNAL 1.1V/2.56V
TEMPERATURE
8-BIT DATA BUS
ADC CTRL. & STATUS B
REFERENCE
SENSOR
REGISTER (ADCSRB)
ADC4
INPUT
INPUT
MUX
NEG.
MUX
ADC MULTIPLEXER
MUX DECODER
SELECT (ADMUX)
+
-
SINGLE ENDED / DIFFERENTIAL SELECTION
GAIN
AMPLIFIER
10-BIT DAC
ADC CTRL. & STATUS A
REGISTER (ADCSRA)
ADC CONVERSION
COMPLETE IRQ
PRESCALER
CONVERSION LOGIC
ADTS[2:0]
INTERRUPT
TRIGGER
SELECT
FLAGS
SAMPLE & HOLD
COMPARATOR
15
+
-
ADC DATA REGISTER
(ADCH/ADCL)
ADC MULTIPLEXER
OUTPUT
7598H–AVR–07/09
0