Datasheet

53
2490R–AVR–02/2013
ATmega64(L)
2. 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 guar-
antees that a Brown-out Reset will occur before V
CC
drops to a voltage where correct
operation of the microcontroller is no longer guaranteed. The test is performed using BOD-
LEVEL=1 for ATmega64L and BODLEVEL=0 for ATmega64. BODLEVEL=1 is not applicable
for ATmega64.
Power-on Reset A Power-on Reset (POR) pulse is generated by an On-chip Detection circuit. The detection level
is defined in Table 19. The POR is activated whenever V
CC
is below the detection level. The
POR circuit can be used to trigger the Start-up Reset, as well as to detect a failure in supply
voltage.
A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the
Power-on Reset threshold voltage invokes the delay counter, which determines how long the
device is kept in RESET after V
CC
rise. The RESET signal is activated again, without any delay,
when V
CC
decreases below the detection level.
Figure 23. MCU Start-up, RESET
Tied to V
CC
Figure 24. MCU Start-up, RESET Extended Externally
V
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
CC
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
V
CC