Atmel ATmega8535L - Power-on Reset

38
ATmega8535(L)
2502K–AVR–10/06
3. 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.
The test is performed using BODLEVEL = 1 for ATmega8535L and BODLEVEL = 0
for ATmega8535. BODLEVEL = 1 is not applicable for ATmega8535.
Power-on Reset A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detec-
tion level is defined in Table 15. 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. Reach-
ing 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 16. MCU Start-up, RESET
Tied to V
CC
Figure 17. 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