Datasheet

25
2586D–AVR–02/06
ATtiny25/45/85
Figure 7-3. Crystal Oscillator Connections
The Oscillator can operate in three different modes, each optimized for a specific frequency
range. The operating mode is selected by the fuses CKSEL3..1 as shown in Table 7-3.
Notes: 1. This option should not be used with crystals, only with ceramic resonators.
The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown in Table
7-4.
Table 7-3. Crystal Oscillator Operating Modes
CKSEL3:1 Frequency Range (MHz)
Recommended Range for Capacitors C1 and
C2 for Use with Crystals (pF)
100
(1)
0.4 - 0.9 –
101 0.9 - 3.0 12 - 22
110 3.0 - 8.0 12 - 22
111 8.0 - 12 - 22
Table 7-4. Start-up Times for the Crystal Oscillator Clock Selection
CKSEL0 SUT1:0
Start-up Time from
Power-down
Additional Delay
from Reset
(V
CC
= 5.0V) Recommended Usage
0 00 258 CK
(1)
14CK + 4.1 ms
Ceramic resonator, fast
rising power
0 01 258 CK
(1)
14CK + 65 ms
Ceramic resonator, slowly
rising power
0 10 1K (1024) CK
(2)
14CK
Ceramic resonator, BOD
enabled
0 11 1K (1024)CK
(2)
14CK + 4.1 ms
Ceramic resonator, fast
rising power
1 00 1K (1024)CK
(2)
14CK + 65 ms
Ceramic resonator, slowly
rising power
1 01 16K (16384) CK 14CK
Crystal Oscillator, BOD
enabled
1 10 16K (16384) CK 14CK + 4.1 ms
Crystal Oscillator, fast
rising power
1 11 16K (16384) CK 14CK + 65 ms
Crystal Oscillator, slowly
rising power
XTAL
2
XTAL
1
GND
C2
C1