18.4Clock Characteristics

18.4.1Calibrated Internal RC Oscillator Accuracy

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 Figure 19-50 on page 148, Figure 19-51 on page 148, Figure 19-52 on page 149, Figure 19-53 on page 149, Figure 19-54 on page 150, and Figure 19-55 on page 150.

Table 18-2.	Calibration Accuracy of Internal RC Oscillator
Calibration					Accuracy at given Voltage
Method		Target Frequency	V	Temperature	& Temperature(1)
			CC
Factory		4.8 / 9.6 MHz	3V	25°C	±10%
Calibration
		Fixed frequency within:	Fixed voltage within:	Fixed temperature
User			1.8V – 5.5V(2)	within:	±2%
		4 – 5 MHz / 8 – 10 MHz
Calibration			2.7V – 5.5V(3)	-40°C to +85°C

Notes: 1. Accuracy of oscillator frequency at calibration point (fixed temperature and fixed voltage).

2.Voltage range for ATtiny13V.

3.Voltage range for ATtiny13.

18.4.2External Clock Drive

Figure 18-3. External Clock Drive Waveform

VIH1

VIL1

Table 18-3.		External Clock Drive
			VCC = 1.8 - 5.5V		VCC = 2.7 - 5.5V		VCC = 4.5 - 5.5V
Symbol		Parameter	Min.	Max.	Min.	Max.	Min.	Max.	Units
1/tCLCL		Clock Frequency	0	4	0	10	0	20	MHz
tCLCL		Clock Period	250		100		50		ns
tCHCX		High Time	100		40		20		ns
tCLCX		Low Time	100		40		20		ns
tCLCH		Rise Time		2.0		1.6		0.5	µs
tCHCL		Fall Time		2.0		1.6		0.5	µs
tCLCL		Change in period from one clock cycle to the next		2		2		2	%

118 ATtiny13

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