
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
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
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
(VCC = 5.0V)
CKSEL0
SUT1..0
BOD enabled
1K CK
000
Fast rising power
1K CK
001
Slowly rising power
1K CK
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
TOSC2
TOSC1