AT90PWM2B-16SE ATMEL [ATMEL Corporation], AT90PWM2B-16SE Datasheet - Page 32

• Manufacturer Part Number: AT90PWM2B-16SE
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

7.5
32
Calibrated Internal RC Oscillator
AT90PWM2/3/2B/3B
The Oscillator can operate in three different modes, each optimized for a specific frequency
range. The operating mode is selected by the fuses CKSEL3..1 as shown in
Table 7-4.
Notes:
The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown in
7-5.
Table 7-5.
Notes:
By default, the Internal RC OScillator provides an approximate 8.0 MHz clock. Though voltage
and temperature dependent, this clock can be very accurately calibrated by the user. The device
is shipped with the CKDIV8 Fuse programmed. See
more details.
CKSEL0
CKSEL3..1
100
0
0
0
0
1
1
1
1
101
110
111
(2)
1. The frequency ranges are preliminary values. Actual values are TBD.
2. This option should not be used with crystals, only with ceramic resonators.
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
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
Crystal Oscillator Operating Modes
Start-up Times for the Oscillator Clock Selection
00
01
10
11
00
01
10
11
Frequency Range
Start-up Time from
Power-down and
8.0 -16.0
0.4 - 0.9
0.9 - 3.0
3.0 - 8.0
Power-save
258 CK
258 CK
1K CK
1K CK
1K CK
16K CK
16K CK
16K CK
(1)
(2)
(2)
(2)
(1)
(1)
(MHz)
Additional Delay
Recommended Range for Capacitors C1 and
14CK + 4.1 ms
14CK + 4.1 ms
14CK + 4.1 ms
14CK + 65 ms
14CK + 65 ms
14CK + 65 ms
(V
from Reset
“System Clock Prescaler” on page 37
CC
14CK
14CK
= 5.0V)
C2 for Use with Crystals (pF)
12 - 22
12 - 22
12 - 22
Recommended Usage
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
–
Table
4317J–AVR–08/10
7-4.
Table
for