ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 32

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

32
Atmel ATmega48PA/88PA/168PA [Preliminary]
The Low-frequency Crystal Oscillator provides an internal load capacitance, see
each TOSC pin.
Table 9-8.
The capacitance (Ce + Ci) needed at each TOSC pin can be calculated by using:
where:
Crystals specifying load capacitance (CL) higher than 6pF, 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
in
Table 9-9.
Table 9-10.
C
Note:
CKSEL3...0
ATmega48PA/88PA/168PA
Table
SUT1...0
=
0100
– 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
– CS - is the total stray capacitance for one TOSC pin.
0101
2
00
01
10
11
(1)
CL C
9-9.
1. This option should only be used if frequency stability at start-up is not important for the
Device
Atmel
–
application
Capacitance for Low-frequency Oscillator
S
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
Figure 9-2 on page
Power-down and Power-save
Table
Start-up Time from
4 CK + 4.1ms
4 CK + 65ms
9-10. Start-up times are determined by the SUT Fuses as shown
32kHz Osc. Type
32K CK
1K CK
4 CK
System Osc.
Timer Osc.
Table 9-8
28.
CC
= 5.0V)
Reserved
Cap(Xtal1/Tosc1)
Recommended Usage
Stable frequency at start-up
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Figure 9-2 on page 28
18pF
18pF
Cap(Xtal2/Tosc2)
9223B–AVR–09/11
8pF
8pF
Table 9-8
at