ATMEGA48V_09 ATMEL [ATMEL Corporation], ATMEGA48V_09 Datasheet - Page 46

• Manufacturer Part Number: ATMEGA48V_09
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

10.4
10.5
46
External Reset
Brown-out Detection
ATmega48/88/168
Figure 10-3. 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
can be disabled by the RSTDISBL fuse, see
Figure 10-4. External Reset During Operation
ATmega48/88/168 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V
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
V
value below the trigger level (V
vated. When V
starts the MCU after the Time-out period t
The BOD circuit will only detect a drop in V
ger than t
BOT
INTERNAL
TIME-OUT
+ V
RESET
RESET
HYST
BOD
V
CC
CC
/2 and V
given in
CC
increases above the trigger level (V
BOT-
“System and Reset Characteristics” on page
= V
V
“System and Reset Characteristics” on page
POT
BOT
BOT-
- V
HYST
in
Figure
/2.When the BOD is enabled, and V
TOUT
CC
Table 27-6 on page
if the voltage stays below the trigger level for lon-
has expired.
10-5), the Brown-out Reset is immediately acti-
V
RST
t
TOUT
BOT+
TOUT
in
– has expired. The External Reset
Figure
286.
RST
306.
– on its positive edge, the
10-5), the delay counter
306) will generate a
CC
decreases to a
2545R–AVR–07/09
BOT+
CC
=