atmega3250v-8auatmega325v-8ai ATMEL Corporation, atmega3250v-8auatmega325v-8ai Datasheet - Page 42

• Manufacturer Part Number: atmega3250v-8auatmega325v-8ai
• Description: Atmega3250 8-bit Microcontroller With In-system Programmable Flash
• Manufacturer: ATMEL Corporation

11.4
11.5
42
External Reset
Brown-out Detection
ATmega325/3250/645/6450
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
reset, 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
delay counter starts the MCU after the Time-out period – t
Figure 11-4. External Reset During Operation
ATmega325/3250/645/6450 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
5 on page
The BOD circuit will only detect a drop in V
longer 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
V
BOT
43), the delay counter starts the MCU after the Time-out period t
CC
CC
BOD
+ V
given in
HYST
/2 and V
“System and Reset Characteristics” on page
V
“System and Reset Characteristics” on page
POT
BOT-
= V
CC
BOT
increases above the trigger level (V
CC
- V
V
BOT-
RST
if the voltage stays below the trigger level for
HYST
t
TOUT
in
/2. When the BOD is enabled, and V
Figure 11-5 on page
TOUT
– has expired.
RST
– on its positive edge, the
300.
300) will generate a
TOUT
43), the Brown-out
BOT+
has expired.
2570L–AVR–08/07
in
Figure 11-
CC