ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 34

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

Table 9-9.
8285D–AVR–06/11
ATmega165A/PA/325A/PA/3250A/PA/645
A/P/6450A/P
Capacitance for Low-Frequency Crystal Oscillator
Device
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
Table 9-8.
Note:
The capacitance (Ce + Ci) needed at each TOSC pin can be calculated by using:
where:
Ce - is optional external capacitors as described in
Ci - is the pin capacitance in
CL - is the load capacitance for a 32.768kHz crystal specified by the crystal vendor.
C
Crystals specifying load capacitance (CL) higher than the ones given in the
34, require external capacitors applied as described in
The Low-frequency Crystal Oscillator must be selected by setting the CKSEL Fuses to “0110” or
“0111” as shown in
Table
Table 9-10.
Table 9-11.
Note:
S
CKSEL3...
SUT1..0
- is the total stray capacitance for one TOSC pin.
0110
0111
00
01
10
11
0
9-10.
(1)
1. Maximum ESR is typical value based on characterization
1. This option should only be used if frequency stability at start-up is not important for the
application
Maximum ESR Recommendation for 32.768kHz Watch Crystal
ATmega325A/325PA/3250A/3250PA/645A/645P/6450A/6450P
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Additional Delay from Reset (V
Crystal CL (pF)
32kHz Osc. Type
Table
Power-down and Power-save
System Osc.
12.5
Timer Osc.
6.5
9.0
Start-up Time from
9-11. Start-up times are determined by the SUT Fuses as shown in
14 CK + 65ms
14 CK + 4ms
Table 9-9 on page 34
32K CK
1K CK
14 CK
Ce
+
Ci
CC
=
Cap (Xtal1/Tosc1)
= 5.0V)
2 CL
⋅
Reserved
Figure 9-2 on page 32
16pF
16pF
–
Figure 9-2 on page
C
s
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Recommended Usage
Stable frequency at start-up
Max ESR [kΩ]
75
65
30
Cap (Xtal2/Tosc2)
32.
Table 9-9 on page
(1)
6pF
6pF
34