atmega32u4-16mu ATMEL Corporation, atmega32u4-16mu Datasheet - Page 29

• Manufacturer Part Number: atmega32u4-16mu
• Description: Atmega32u4 8-bit Avr Microcontroller With 32k Bytes Of Isp Flash And Usb Controller
• Manufacturer: ATMEL Corporation

7766A–AVR–03/08
electromagnetic noise of the environment. Some initial guidelines for choosing capacitors for
use with crystals are given in
the manufacturer should be used.
Figure 6-2.
The Low Power Oscillator can operate in three different modes, each optimized for a specific fre-
quency range. The operating mode is selected by the fuses CKSEL[3..1] as shown in
Table 6-3.
Notes:
The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown in
6-4.
Table 6-4.
Oscillator Source /
Power Conditions
Ceramic resonator, fast
rising power
Ceramic resonator,
slowly rising power
Ceramic resonator,
BOD enabled
Ceramic resonator, fast
rising power
Ceramic resonator,
slowly rising power
Frequency Range
1. The frequency ranges are preliminary values. Actual values are TBD.
2. This option should not be used with crystals, only with ceramic resonators.
3. If 8 MHz frequency exceeds the specification of the device (depends on V
Fuse can be programmed in order to divide the internal frequency by 8. It must be ensured
that the resulting divided clock meets the frequency specification of the device.
8.0 - 16.0
0.4 - 0.9
0.9 - 3.0
3.0 - 8.0
Crystal Oscillator Connections
Low Power Crystal Oscillator Operating Modes
Start-up Times for the Low Power Crystal Oscillator Clock Selection
(1)
(MHz)
Start-up Time from
Power-down and
Power-save
Table
258 CK
258 CK
1K CK
1K CK
1K CK
CKSEL3..1
6-3. For ceramic resonators, the capacitor values given by
C2
C1
100
101
110
111
(2)
Additional Delay
14CK + 4.1 ms
14CK + 4.1 ms
14CK + 65 ms
14CK + 65 ms
Recommended Range for Capacitors
(V
from Reset
CC
14CK
= 5.0V)
XTAL2
XTAL1
GND
(2)
C1 and C2 (pF)
(3)
(1)
(2)
(1)
(2)
12 - 22
12 - 22
12 - 22
–
CKSEL0
ATmega32U4
0
0
0
0
1
CC
SUT1..0
), the CKDIV8
00
01
10
00
11
Table
Table
6-3.
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