Datasheet

308
8023F–AVR–07/09
ATmega325P/3250P
26.5 System and Reset Characterizations
26.6 Standard Power-on Reset
This implementation of power-on reset existed in early versions of ATmega325P/3250P. The
table below describes the characteristics of this power-on reset and it is valid for the following
devices, only:
• ATmega325P revision B and older
• ATmega3250P revision B and older
Note: 1. The Power-on Reset will not work unless the supply voltage has been below V
POT
(falling)
26.7 Enhanced Power-on Reset
This implementation of power-on reset exists in newer versions of ATmega325P/3250P. The
table below describes the characteristics of this power-on reset and it is valid for the following
devices only:
• ATmega325P revision C and newer
• ATmega3250P revision C and newer
Table 26-3. Reset, Brown-out, and Internal Voltage Reference Characteristics
Symbol Parameter Condition Min Typ Max Units
V
RST
RESET Pin Threshold Voltage V
CC
= 3V 0.2 V
CC
0.85 V
CC
V
t
RST
Minimum pulse width on RESET Pin V
CC
= 3V 800 ns
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
= 2.7V,
T
A
= 25°C
1.0 1.1 1.2 V
t
BG
Bandgap reference start-up time
V
CC
= 2.7V,
T
A
= 25°C
40 70 µs
I
BG
Bandgap reference current consumption
V
CC
= 2.7V,
T
A
= 25°C
15 µA
Table 26-4. Reset, Brown-out, and Internal Voltage Reference Characteristics,
T
A
= -40°C to 85°C
Symbol Parameter 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
SR
ON
Power-on Slope Rate 0.01 4.5 V/ms