ATmega8A Atmel Corporation, ATmega8A Datasheet - Page 40

• Manufacturer Part Number: ATmega8A
• Manufacturer: Atmel Corporation

Specifications of ATmega8A

• 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
• Pwm Channels: 3
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

10.2.4
10.3
10.3.1
8159D–AVR–02/11
Internal Voltage Reference
Watchdog Reset
Voltage Reference Enable Signals and Start-up Time
Figure 10-5. Brown-out Reset During Operation
When the Watchdog times out, it will generate a short reset pulse of 1 CK cycle duration. On the
falling edge of this pulse, the delay timer starts counting the time-out period t
41
Figure 10-6. Watchdog Reset During Operation
ATmega8A 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
turned on. The reference is on during the following situations:
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
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.
for details on operation of the Watchdog Timer.
ACBG bit in ACSR).
CC
INTERNAL
TIME-OUT
RESET
RESET
V
CC
Table 25-3 on page
V
CK
BOT-
247. To save power, the reference is not always
V
t
TOUT
BOT+
ATmega8A
TOUT
. Refer to
page
40