Datasheet

307
2545T–AVR–05/11
ATmega48/88/168
29.5 System and reset characteristics
Note: 1. The power-on reset will not work unless the supply voltage has been below V
POT
(falling).
Notes: 1. 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 = 110 and BODLEVEL = 101 for Atmel ATmega48V/88V/168V, and BODLEVEL = 101 and BODLEVEL = 100
for Atmel ATmega48/88/168.
Table 29-3. Reset, brown-out and internal voltage characteristics.
Symbol Parameter Condition Min. Typ. Max. Units
V
POT
Power-on reset threshold voltage (rising) 0.7 1.0 1.4
V
Power-on reset threshold voltage (falling)
(1)
0.05 0.9 1.3
V
PONSR
Power-on slope rate 0.01 4.5 V/ms
V
RST
RESET pin threshold voltage 0.2V
CC
0.9V
CC
V
t
RST
Minimum pulse width on RESET pin 2.5 µs
V
HYST
Brown-out detector hysteresis 50 mV
t
BOD
Min pulse width on brown-out reset 2 µs
V
BG
Bandgap reference voltage
V
CC
= 2.7
T
A
= 25°C
1.0 1.1 1.2 V
t
BG
Bandgap reference start-up time
V
CC
= 2.7
T
A
= 25°C
40 70 µs
I
BG
Bandgap reference current consumption
V
CC
= 2.7
T
A
= 25°C
10 µA
Table 29-4. BODLEVEL fuse coding
(1)
.
BODLEVEL 2:0 Fuses Min. V
BOT
Typ. V
BOT
Max. V
BOT
Units
111 BOD disabled
110 1.7 1.8 2.0
V101 2.5 2.7 2.9
100 4.1 4.3 4.5
011
Reserved
010
001
000