ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 33

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

9.6
8285D–AVR–06/11
Low-frequency Crystal Oscillator
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
Table 9-6.
Notes:
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
t a k e n i n t o c o n s i d e r a t i o n . B o t h v a l u e s a r e s p e c i f i e d b y t h e c r y s t a l v e n d o r .
ATmega165A/165PA/325A/325PA/3250A/3250PA/645A/645P/6450A/6450P oscillator is opti-
mized for very low power consumption, and thus when selecting crystals, see
maximum ESR recommendations on 9pF and 6.5pF crystals.
Table 9-7.
Note:
The Low-frequency Crystal Oscillator provides an internal load capacitance, see
page 34
ATmega325A/325PA/3250A/3250PA/645A/645P/6450A/6450P oscillator is optimized for very
low power consumption, and thus when selecting crystals, see
mum ESR recommendations on 6.5 pF, 9.0 pF and 12.5 pF crystals.
CKSEL0
0
1
1
1
1
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. Maximum ESR is typical value based on characterization
at each TOSC pin.
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.
SUT1:0
Start-up Times for the Crystal Oscillator Clock Selection (Continued)
Maximum ESR Recommendation for 32.768kHz Watch Crystal
ATmega165A/ATmega165PA
11
00
01
10
11
Crystal CL (pF)
6.5
9
Start-up Time from
Power-down and
Power-save
1K CK
1K CK
16K CK
16K CK
16K CK
(2)
(2)
Additional Delay
14CK + 4.1ms
14CK + 4.1ms
14CK + 65ms
14CK + 65ms
(V
from Reset
CC
14CK
= 5.0V)
Table 9-8 on page 34
Max ESR [kΩ]
Recommended Usage
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Crystal Oscillator, BOD
enabled
Crystal Oscillator, fast
rising power
Crystal Oscillator, slowly
rising power
60
35
(1)
Table 9-7
Table 9-9 on
for maxi-
for
33