50
2513L–AVR–03/2013
ATmega162/V
Brown-out Detection
ATmega162 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V
CC level dur-
ing operation by comparing it to a fixed trigger level. The trigger level for the BOD can be
selected by the BODLEVEL Fuses. 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 + VHYST/2 and VBOT- = VBOT - VHYST/2.
Notes:
1. VBOT may be below nominal minimum operating voltage for some devices. For devices where
this is the case, the device is tested down to V
CC = VBOT during the production test. This guar-
antees that a Brown-out Reset will occur before VCC drops to a voltage where correct
operation of the microcontroller is no longer guaranteed. This test is performed using BOD-
LEVEL = 110 for ATmega162V, BODLEVEL = 101 and BODLEVEL = 100 for ATmega162.
2. For ATmega162V. Otherwise reserved.
When the BOD is enabled and V
CC decreases to a value below the trigger level (VBOT- in Figure 25), the Brown-out Reset is immediately activated. When V
CC increases above the trigger level
(V
BOT+ in Figure 25), the delay counter starts the MCU after the Time-out period tTOUT has expired.
The BOD circuit will only detect a drop in V
CC if the voltage stays below the trigger level for lon-
ger than t
Table 19. BODLEVEL Fuse Coding
BODLEVEL Fuses [2:0]
Typ. VBOT
Max. VBOT
Units
111
BOD Disabled
1.7
1.8
2.0
V
101
2.5
2.7
2.9
100
4.1
4.3
4.5
2.1
2.3
2.5
010
Reserved
001
000
Table 20. Brown-out Hysteresis
Symbol
Parameter
Min.
Typ.
Max.
Units
VHYST
Brown-out Detector hysteresis
50
mV
t
BOD
Min Pulse Width on Brown-out Reset
2
s