ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 31

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

9.5
9223B–AVR–09/11
Low Frequency Crystal Oscillator
Table 9-6.
The Low-frequency Crystal Oscillator is optimized for use with a 32.768kHz watch crystal.
When selecting crystals, load capacitance and crystal’s Equivalent Series Resistance, ESR
must be taken into consideration. Both values are specified by the crystal vendor. Atmel
ATmega48PA/88PA/168PA oscillator is optimized for very low power consumption, and thus
when selecting crystals, see
and 12.5pF crystals
Table 9-7.
Oscillator Source / Power
Conditions
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
Notes:
Note:
Atmel ATmega48PA/88PA/168PA [Preliminary]
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 sta-
1. Maximum ESR is typical value based on characterization
the device, and only if frequency stability at start-up is not important for the application.
These options are not suitable for crystals.
bility 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.
Start-up Times for the Full Swing Crystal Oscillator Clock Selection
Maximum ESR Recommendation for 32.768kHz Crystal
Crystal CL (pF)
12.5
6.5
9.0
Start-up Time from
Table 9-7
Power-down and
Power-save
16K CK
16K CK
16K CK
258 CK
258 CK
1K CK
1K CK
1K CK
for maximum ESR recommendations on 6.5pF, 9.0pF
Additional Delay from
14CK + 4.1ms
14CK + 4.1ms
14CK + 65ms
14CK + 65ms
14CK + 4.1ms
14CK + 65ms
(V
CC
14CK
Reset
14CK
= 5.0V)
(2)
Max ESR [k ]
(1)
(2)
(1)
(2)
75
65
30
CKSEL0
(1)
0
0
0
0
1
1
1
1
SUT1...0
00
01
10
11
00
01
10
11
31
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