Datasheet

35
7674F–AVR–09/09
ATmega164P/324P/644P
Figure 7-3. Crystal Oscillator Connections
Table 7-8. Low-frequency Crystal Oscillator Internal load Capacitance
Crystals specifying load capacitance (CL) higher than 8.0 pF, require external capacitors applied
as described in Figure 7-2 on page 32.
To find suitable load capacitance for a 32.768 kHz crysal, please consult the crystal datasheet.
When this oscillator is selected, start-up times are determined by the SUT Fuses and CKSEL0
as shown in Table 7-9.
Note: 1. These options should only be used if frequency stability at start-up is not important for the
application.
Min. (pF) Typ. (pF) Max. (pF)
TBD 8.0 TBD
Table 7-9. Start-up Times for the Low Frequency Crystal Oscillator Clock Selection
Power Conditions
Start-up Time from
Power-down and
Power-save
Additional Delay
from Reset
(V
CC
= 5.0V) CKSEL0 SUT1..0
BOD enabled 1K CK 14CK
(1)
000
Fast rising power 1K CK 14CK + 4.1 ms
(1)
001
Slowly rising power 1K CK 14CK + 65 ms
(1)
010
Reserved 0 11
BOD enabled 32K CK 14CK 1 00
Fast rising power 32K CK 14CK + 4.1 ms 1 01
Slowly rising power 32K CK 14CK + 65 ms 1 10
Reserved 1 11
TOSC
2
TOSC1