Datasheet

327
2490R–AVR–02/2013
ATmega64(L)
External Clock
Drive Waveforms
Figure 155. External Clock Drive Waveforms
External Clock
Drive
Note: 1. Refer to “External Clock” on page 44 for details.
Notes: 1. R should be in the range 3 k - 100 k, and C should be at least 20 pF. 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.
V
IL1
V
IH1
Table 131. External Clock Drive
(1)
Symbol Parameter
V
CC
= 2.7V to 5.5VV
CC
= 4.5V to 5.5V
UnitsMin Max Min Max
1/t
CLCL
Oscillator Frequency 0 8 0 16 MHz
t
CLCL
Clock Period 125 62.5
nst
CHCX
High Time 50 25
t
CLCX
Low Time 50 25
t
CLCH
Rise Time 1.6 0.5
µs
t
CHCL
Fall Time 1.6 0.5
t
CLCL
Change in period from
one clock cycle to the
next
22%
Table 132. External RC Oscillator, Typical Frequencies
R [k]
(1)
C [pF] f
(2)
31.5 20 650 kHz
6.5 20 2.0 MHz