ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 28

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

7.5
28
Low-frequency Crystal Oscillator
Atmel ATtiny24/44/84 [Preliminary]
Table 7-4.
Notes:
To use a 32.768kHz 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 7-5.
Notes:
SUT1..0
CKSEL0
00
01
10
11
0
0
0
0
1
1
1
1
7-5.
1. These options should only be used when not operating close to the maximum frequency of
2. These options are intended for use with ceramic resonators and will ensure frequency stabil-
1. These options should only be used if frequency stability at start-up is not important for the
the device, and only if frequency stability at start-up is not important for the application.
These options are not suitable for crystals.
ity at start-up. They can also be used with crystals when not operating close to the maximum
frequency of the device, and if frequency stability at start-up is not important for the
application.
application.
Start-up Time from Power
Figure
Down and Power Save
SUT1..0
Start-up Times for the Crystal Oscillator Clock Selection
Start-up Times for the Low Frequency Crystal Oscillator Clock Selection
00
01
10
11
00
01
10
11
7-2. See the 32kHz Crystal Oscillator Application Note for details on oscil-
1K CK
1K CK
32K CK
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 + 4.1ms
14CK + 4.1ms
14CK + 4.1ms
14CK + 65ms
14CK + 65ms
14CK + 65ms
(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
7701E–AVR–02/11