ATMEGA128-16AU SL383 Atmel, ATMEGA128-16AU SL383 Datasheet - Page 41

• Manufacturer Part Number: ATMEGA128-16AU SL383
• Manufacturer: Atmel

External RC
Oscillator
2467S–AVR–07/09
For timing insensitive applications, the External RC configuration shown in
used. The frequency is roughly estimated by the equation f = 1/(3RC). C should be at least 22
pF. By programming the CKOPT fuse, the user can enable an internal 36 pF capacitor between
XTAL1 and GND, thereby removing the need for an external capacitor. For more information on
Oscillator operation and details on how to choose R and C, refer to the External RC Oscillator
application note.
Figure 20. External RC Configuration
The Oscillator can operate in four different modes, each optimized for a specific frequency
range. The operating mode is selected by the fuses CKSEL3..0 as shown in
Table 11. External RC Oscillator Operating Modes
When this Oscillator is selected, start-up times are determined by the SUT fuses as shown in
Table
Table 12. Start-Up Times for the External RC Oscillator Clock Selection
Note:
SUT1..0
00
01
10
11
12.
1. This option should not be used when operating close to the maximum frequency of the device.
CKSEL3..0
Start-up Time from
Power-down and
0101
0110
0111
1000
Power-save
6 CK
18 CK
18 CK
18 CK
(1)
R
C
V
CC
Additional Delay
(V
from Reset
CC
4.1 ms
4.1 ms
65 ms
NC
= 5.0V)
–
Frequency Range (MHz)
Recommended Usage
BOD enabled
Fast rising power
Slowly rising power
Fast rising power or BOD enabled
8.0 - 12.0
0.1 - 0.9
0.9 - 3.0
3.0 - 8.0
XTAL2
XTAL1
GND
ATmega128
Table
Figure 20
11.
can be
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