4 clock characteristics, 1 calibrated internal oscillator accuracy, 2 external clock drive – Rainbow Electronics ATtiny43U User Manual
Page 157: Table, Calibration in, Frequencies as specified in, Table 20
157
8048B–AVR–03/09
20.4
Clock Characteristics
20.4.1
Calibrated Internal Oscillator Accuracy
It is possible to manually calibrate the internal oscillator to be more accurate than default factory calibration. Please note
that the oscillator frequency depends on temperature and voltage.
Notes:
1. Accuracy of oscillator frequency at calibration point (fixed temperature and fixed voltage).
20.4.2
External Clock Drive
Figure 20-2. External Clock Drive Waveforms
Table 20-2.
Calibration Accuracy of Internal Oscillator
Calibration
Method
Target Frequency
V
CC
Temperature
Accuracy at given Voltage
& Temperature
Factory
Calibration
8.0 MHz
3V
25
°
C
±10%
User
Calibration
Fixed frequency within:
7.3 - 8.1 MHz
Fixed voltage within:
1.8V - 5.5V
Fixed temperature within:
-40
°
C - 85
°
C
±1%
Table 20-3.
External Clock Drive Characteristics
Symbol
Parameter
V
CC
= 1.8 - 5.5V
V
CC
= 2.7 - 5.5V
Units
Min.
Max.
Min.
Max.
1/t
CLCL
Clock Frequency
0
4
0
8
MHz
t
CLCL
Clock Period
250
125
ns
t
CHCX
High Time
100
50
ns
t
CLCX
Low Time
100
50
ns
t
CLCH
Rise Time
2.0
1.6
μ
s
t
CHCL
Fall Time
2.0
1.6
μ
s
Δ
t
CLCL
Period change from clock cycle to next
2
2
%
V
IL1
V
IH1