Datasheet

249
ATtiny828 [DATASHEET]
8371A–AVR–08/12
24.3 Speed
The maximum operating frequency of the device is dependent on supply voltage, V
CC
. The relationship between supply
voltage and maximum operating frequency is piecewise linear, as shown in Figure 101.
Figure 101. Maximum Operating Frequency vs. Supply Voltage
24.4 Clock Characteristics
24.4.1 Accuracy of Calibrated Internal Oscillator
It is possible to manually calibrate the internal oscillator to be more accurate than default factory calibration. Note that the
oscillator frequency depends on temperature and voltage. Voltage and temperature characteristics can be found in
“Internal Oscillator Speed” on page 293.
Table 104. Calibration Accuracy of Internal 8MHz Oscillator
Notes: 1. Accuracy of oscillator frequency at calibration point (fixed temperature and voltage).
2. See device ordering codes on page 303 for alternatives.
3. Not available in ATtiny828R devices.
24.4.2 Accuracy of Calibrated 32kHz Oscillator
It is possible to manually calibrate the internal 32kHz oscillator to be more accurate than default factory calibration. Note
that the oscillator frequency depends on temperature and voltage. Voltage and temperature characteristics can be found
in “Internal Oscillator Speed” on page 293.
4 MHz
1.8V 5.5V
4.5V
20 MHz
2.7V
10 MHz
2 MHz
1.7V
Calibration
Method Target Frequency V
CC
Temperature Accuracy
(1)
Factory
Calibration
8.0 MHz 3V 25°C
±2%
(2)
±10%
(2)
User
Calibration
(3)
Within:
7.3 – 8.1 MHz
Within:
1.7V – 5.5V
Within:
-40°C to +85°C
±1%