Brown-out detection, Atmega162/v – Rainbow Electronics ATmega162V User Manual
Page 49
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ATmega162/V
2513E–AVR–09/03
Brown-out Detection
ATmega162 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 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
+ V
HYST
/2 and V
BOT-
= V
BOT
- V
HYST
/2.
Notes:
1. V
BOT
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
= V
BOT
during the
production test. This guarantees that a Brown-out Reset will occur before V
CC
drops
to a voltage where correct operation of the microcontroller is no longer guaranteed.
This test is performed using BODLEVEL = 110 for ATmega162V, BODLEVEL = 101
for ATmega162L, 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 (V
BOT-
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 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 18.
Table 19. BODLEVEL Fuse Coding
BODLEVEL Fuses [2:0]
Min. V
BOT
Typ. V
BOT
Max. V
BOT
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
V
HYST
Brown-out Detector hysteresis
50
mV
t
BOD
Min Pulse Width on Brown-out Reset
2
µs