Datasheet

53
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
When the BOD is enabled, and V
CC
decreases to a value below the trigger level (V
BOT-
in Figure 8-5), the
Brown-out Reset is immediately activated. When V
CC
increases above the trigger level (V
BOT+
in Figure 8-5), 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 Table 29-3 on page 386.
Figure 8-5. Brown-out Reset During Operation
8.6 Watchdog Reset
When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On the falling edge
of this pulse, the delay timer starts counting the Time-out period t
TOUT
. For details on operation of the Watchdog
Timer, see “Watchdog Timer” on page 55.
Table 8-1. BODLEVEL Fuse Coding
BODLEVEL 2..0 Fuses Min. V
BOT
Typ. V
BOT
Max. V
BOT
Units
111 BOD Disabled
110 1.8 2.0 2.2
V
101 2.0 2.2 2.4
100 2.2 2.4 2.6
011 2.4 2.6 2.8
010 3.2 3.4 3.6
001 3.3 3.5 3.7
000 4.0 4.3 4.5
Table 8-2. BOD characteristics
Symbol Parameter Min. Typ. Max. Units
V
HYST
Brown-out Detector Hysteresis 50 mV
t
BOD
Min Pulse Width on Brown-out Reset ns
V
CC
RESET
TIME-OUT
INTERNAL
RESET
V
BOT-
V
BOT+
t
TOUT