ATA8741 ATMEL Corporation, ATA8741 Datasheet - Page 44

• Manufacturer Part Number: ATA8741
• Manufacturer: ATMEL Corporation

14.5
44
Low-frequency Crystal Oscillator
ATA8741
Table 14-4.
Notes:
To use a 32.768 kHz watch crystal as the clock source for the device, the low-frequency crystal
oscillator must be selected by setting CKSEL fuses to ‘0110’. The crystal should be connected
as shown in
lator operation and how to choose appropriate values for C1 and C2.
When this oscillator is selected, start-up times are determined by the SUT fuses as shown in
Table
Table 14-5.
Notes:
CKSEL0
SUT1..0
00
01
10
11
0
0
0
0
1
1
1
1
14-5.
1. These options should only be used when not operating close to the maximum frequency of the
2. These options are intended for use with ceramic resonators and will ensure frequency stability
1. These options should only be used if frequency stability at start-up is not important for the
device, and only if frequency stability at start-up is not important for the application. These
options are not suitable for crystals.
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.
application.
Figure
Power Down and Power
SUT1..0
Start-up Times for the Crystal Oscillator Clock Selection
Start-up Times for the Low Frequency Crystal Oscillator Clock Selection
Start-up Time from
00
01
10
11
00
01
10
11
14-2. See the 32 kHz Crystal Oscillator Application Note for details on oscil-
1K CK
1K CK
32K CK
Save
Start-up Time from
(1)
(1)
Power-down and
Power-save
258 CK
258 CK
1K CK
1K CK
1K CK
16K CK
16K CK
16K CK
(2)
(2)
(2)
(1)
(1)
Additional Delay from
Reset (V
64 ms
64 ms
4 ms
Reserved
Additional Delay
CC
14CK + 4.1 ms
14CK + 4.1 ms
14CK + 4.1 ms
14CK + 65 ms
14CK + 65 ms
14CK + 65 ms
(V
from Reset
= 5.0V)
CC
14CK
14CK
= 5.0V)
Recommended usage
Fast rising power or BOD
enabled
Slowly rising power
Stable frequency at start-up
Recommended Usage
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Ceramic resonator, BOD
enabled
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Crystal Oscillator, BOD
enabled
Crystal Oscillator, fast
rising power
Crystal Oscillator, slowly
rising power
9140B–INDCO–07/09