ATTINY43U_1 Datasheet, PDF (157/182 Pages) ATMEL Corporation – 8-bit Microcontroller with 4K Bytes In-System Programmable Flash and Boost Converter

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.
Table 20-2. Calibration Accuracy of Internal Oscillator
Calibration
Method
Target Frequency
V_CC
Factory
Calibration
8.0 MHz
3V
User
Calibration
Fixed frequency within:
7.3 - 8.1 MHz
Fixed voltage within:
1.8V - 5.5V
Temperature
Accuracy at given Voltage
& Temperature ⁽¹⁾
25°C
±10%
Fixed temperature within:
-40°C - 85°C
±1%
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
V_IH1
V_IL1
Table 20-3. External Clock Drive Characteristics
Symbol
1/t_CLCL
t_CLCL
t_CHCX
t_CLCX
t_CLCH
t_CHCL
Δt_CLCL
Parameter
Clock Frequency
Clock Period
High Time
Low Time
Rise Time
Fall Time
Period change from clock cycle to next
V_CC = 1.8 - 5.5V
Min.
Max.
0
4
250
100
100
2.0
2.0
2
V_CC = 2.7 - 5.5V
Min.
Max.
0
8
125
50
50
1.6
1.6
2
Units
MHz
ns
ns
ns
μs
μs
%
8048B–AVR–03/09
157