Datasheet

14.2.3. Brown-out Detection
ATmega32A has an On-chip Brown-out Detection (BOD) circuit for monitoring the V
CC
level during
operation by comparing it to a fixed trigger level. The trigger level for the BOD can be selected by the fuse
BODLEVEL to be 2.7V (BODLEVEL unprogrammed), or 4.0V (BODLEVEL programmed). The trigger
level has a hysteresis to ensure spike free Brown-out Detection. The hysteresis on the detection level
should be interpreted as V
BOT+
= V
BOT
+ V
HYST
/2 and V
BOT-
= V
BOT
- V
HYST
/2.
The BOD circuit can be enabled/disabled by the fuse BODEN. When the BOD is enabled (BODEN
programmed), and V
CC
decreases to a value below the trigger level (V
BOT-
in the figure below), the
Brown-out Reset is immediately activated. When V
CC
increases above the trigger level (V
BOT+
in the
figure below), the delay counter starts the MCU after the time-out period t
TOUT
has expired.
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 14-5. Brown-out Reset During Operation
V
CC
RES ET
TIME-OUT
INTERNAL
RES ET
V
BOT-
V
BOT+
t
TOUT
Related Links
System and Reset Characteristics on page 363
14.2.4. 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 14-6. Watchdog Reset During Operation
CK
CC
Atmel ATmega32A [DATASHEET]
Atmel-8155I-ATmega32A_Datasheet_Complete-08/2016
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