Datasheet

29.4.1. Clock characteristics
Table 29-5. Calibration accuracy of internal RC oscillator.
Frequency V
CC
Temperature Calibration accuracy
Factory calibration 8.0MHz 3V 25°C ±10%
User calibration 7.3 - 8.1MHz 1.8 - 5.5V -40°C - 85°C ±1%
29.4.2. External Clock Drive Waveforms
Figure 29-2. External Clock Drive Waveforms
V
IL1
V
IH1
29.4.3. External Clock Drive
Table 29-6. External Clock Drive
Symbol Parameter V
CC
= 1.8 - 5.5V V
CC
= 2.7 - 5.5V V
CC
= 4.5 - 5.5V Units
Min. Max. Min. Max. Min. Max.
1/t
CLCL
Oscillator Frequency 0 4 0 10 0 20 MHz
t
CLCL
Clock Period 250 - 100 - 50 - ns
t
CHCX
High Time 100 - 40 - 20 - ns
t
CLCX
Low Time 100 - 40 - 20 - ns
t
CLCH
Rise Time - 2.0 - 1.6 - 0.5 μs
t
CHCL
Fall Time - 2.0 - 1.6 - 0.5 μs
Δt
CLCL
Change in period from one clock
cycle to the next
- 2 - 2 - 2 %
29.5. System and Reset Characteristics
Table 29-7. Reset, Brown-out and Internal Voltage Characteristics
Symbol Parameter Condition Min. Typ Max Units
V
POT
Power-on Reset Threshold Voltage (rising) 1.1 1.4 1.6 V
Power-on Reset Threshold Voltage (falling)
(1)
0.6 1.3 1.6 V
SR
ON
Power-on Slope Rate 0.01 - 10 V/ms
V
RST
RESET Pin Threshold Voltage 0.2 V
CC
- 0.9 V
CC
V
t
RST
Minimum pulse width on RESET Pin - - 2.5 μs
V
HYST
Brown-out Detector Hysteresis - 50 - mV
Atmel ATmega644PA [DATASHEET]
Atmel-42717C-ATmega644PA_Datasheet_Complete-10/2016
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