8-bit AVR Microcontroller

External Clock Drive

Table 1. External Clock Drive
Symbol	Parameter	V_CC = 2.7V to 5.5V		V_CC = 4.5V to 5.5V		Units
Symbol	Parameter	Min	Max	Min	Max	Units
1/t_CLCL	Oscillator Frequency	0	8	0	16	MHz
t_CLCL	Clock Period	125		62.5		ns
t_CHCX	High Time	50		25		ns
t_CLCX	Low Time	50		25		ns
t_CLCH	Rise Time		1.6		0.5	μs
t_CHCL	Fall Time		1.6		0.5	μs
Δt_CLCL	Change in period from one clock cycle to the next		2		2	%

Table 2. External RC Oscillator, Typical Frequencies
R [kΩ]⁽¹⁾	C [pF]	f⁽²⁾
33	22	650kHz
10	22	2.0MHz

Notes:

1.R should be in the range 3kΩ - 100kΩ, and C should be at least 20pF. The C values given in the table includes pin capacitance. This will vary with package type.
2.The frequency will vary with package type and board layout.