Datasheet

32
2545T–AVR–05/11
ATmega48/88/168
Figure 9-3. Crystal oscillator connections.
Notes: 1. These options should only be used when not operating close to the maximum frequency of the
device, and only if frequency stability at start-up is not important for the application. These
options are not suitable for crystals.
2. These options are intended for use with ceramic resonators and will ensure frequency stability
at start-up. They can also be used with crystals when not operating close to the maximum fre-
quency of the device, and if frequency stability at start-up is not important for the application.
Table 9-6. Start-up times for the full swing crystal oscillator clock selection.
Oscillator source/
power conditions
Start-up time from
power-down and
power-save
Additional delay
from reset
(V
CC
= 5.0V) CKSEL0 SUT1..0
Ceramic resonator,
fast rising power
258CK 14CK + 4.1ms
(1)
000
Ceramic resonator,
slowly rising power
258CK 14CK + 65ms
(1)
001
Ceramic resonator,
BOD enabled
1KCK 14CK
(2)
010
Ceramic resonator,
fast rising power
1KCK 14CK + 4.1ms
(2)
011
Ceramic resonator,
slowly rising power
1KCK 14CK + 65ms
(2)
100
Crystal Oscillator,
BOD enabled
16KCK 14CK 1 01
Crystal Oscillator,
fast rising power
16KCK 14CK + 4.1ms 1 10
Crystal Oscillator,
slowly rising power
16KCK 14CK + 65ms 1 11
XTAL2
XTAL1
GND
C2
C1