ATMEGA48V_11 ATMEL [ATMEL Corporation], ATMEGA48V_11 Datasheet - Page 47

• Manufacturer Part Number: ATMEGA48V_11
• Description: 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

11.4
11.5
2545T–AVR–05/11
External reset
Brown-out detection
Figure 11-3. MCU start-up, RESET extended externally.
An external reset is generated by a low level on the RESET pin. Reset pulses longer than the
minimum pulse width (see
even if the clock is not running. Shorter pulses are not guaranteed to generate a reset. When the
applied signal reaches the reset threshold voltage – V
ter starts the MCU after the time-out period – t
disabled by the RSTDISBL fuse, see
Figure 11-4. External reset during operation.
The Atmel ATmega48/88/168 has an on-chip brown-out detection (BOD) circuit for monitoring
the V
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
decreases to a value below the trigger level (V
reset is immediately activated. When V
on page
The BOD circuit will only detect a drop in V
ger than t
BOT+
INTERNAL
TIME-OUT
CC
= V
RESET
RESET
level during operation by comparing it to a fixed trigger level. The trigger level for the
48), the delay counter starts the MCU after the Time-out period t
BOD
V
BOT
CC
CC
given in
+ V
HYST
“System and reset characteristics” on page
/2 and V
“System and reset characteristics” on page
V
POT
BOT-
Table 28-6 on page
= V
CC
BOT
increases above the trigger level (V
CC
- V
if the voltage stays below the trigger level for lon-
V
BOT-
RST
TOUT
HYST
t
TOUT
in
– has expired. The external reset can be
RST
/2.When the BOD is enabled, and V
Figure 11-5 on page
287.
– on its positive edge, the delay coun-
ATmega48/88/168
307.
307) will generate a reset,
TOUT
48), the brown-out
BOT+
has expired.
in
Figure 11-5
47
CC