Datasheet

The BOD circuit will only detect a drop in V
CC
if the voltage stays below the trigger level for longer than
t
BOD
given in the table in System and Reset Characteristics.
Figure 15-5. Brown-out Reset During Operation
V
CC
RESET
TIME-OUT
INTERNAL
RESET
V
BOT-
V
BOT+
t
TOUT
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System and Reset Characteristics
15.2.4 Watchdog Reset
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
TOUT
. Refer to Watchdog Timer for
details on operation of the Watchdog Timer.
Figure 15-6. Watchdog Reset During Operation
CK
CC
15.3 Internal Voltage Reference
ATmega8A features an internal bandgap reference. This reference is used for Brown-out Detection, 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.
15.3.1 Voltage Reference Enable Signals and Start-up Time
The voltage reference has a start-up time that may influence the way it should be used. The start-up time
is given in the table in System and Reset Characteristics. To save power, the reference is not always
turned on. The reference is on during the following situations:
1. When the BOD is enabled (by programming the BODEN Fuse).
AVR 8-Bit Microcontroller
System Control and Reset
© 2017 Microchip Technology Inc.
Datasheet Complete
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