ATmega8 Atmel Corporation, ATmega8 Datasheet - Page 42

• Manufacturer Part Number: ATmega8
• Manufacturer: Atmel Corporation

Specifications of ATmega8

• Flash (kbytes): 8 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 2
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• 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: No
• 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: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 1
• Pwm Channels: 3
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

Internal Voltage
Reference
Voltage Reference
Enable Signals and
Start-up Time
42
ATmega8(L)
ATmega8 features an internal bandgap reference. This reference is used for Brown-out Detec-
tion, and it can be used as an input to the Analog Comparator or the ADC. The 2.56V reference
to the ADC is generated from the internal bandgap reference.
The voltage reference has a start-up time that may influence the way it should be used. The
start-up time is given in
erence is on during the following situations:
1. When the BOD is enabled (by programming the BODEN Fuse)
2. When the bandgap reference is connected to the Analog Comparator (by setting the
3. When the ADC is enabled
Thus, when the BOD is not enabled, after setting the ACBG bit or enabling the ADC, the user
must always allow the reference to start up before the output from the Analog Comparator or
ADC is used. To reduce power consumption in Power-down mode, the user can avoid the three
conditions above to ensure that the reference is turned off before entering Power-down mode.
Table 16. Internal Voltage Reference Characteristics
Symbol
ACBG bit in ACSR)
V
t
I
BG
BG
BG
Parameter
Bandgap reference voltage
Bandgap reference start-up time
Bandgap reference current consumption
Table
16. To save power, the reference is not always turned on. The ref-
1.15
Min
1.30
Typ
40
10
1.40
Max
70
Units
µA
µs
2486Z–AVR–02/11
V