Atmel AT32UC3L016, Manual

Page: 47 / 88

47
32099DS–06/2010
AT32UC3L016/32/64
7.7.1.2 Crystal Oscillator Characteristics
The following table describes the characteristics for the oscillator when a crystal is connected
between XIN and XOUT as shown in
Figure 7-3 . The user must choose a crystal oscillator
where the crystal load capacitance
C
L
is within the range given in the table. The exact value of C
L
can be found in the crystal datasheet. The capacitance of the external capacitors (C
LEXT
) can
then be computed as follows:
where C
PCB
is the capacitance of the PCB.
Notes: 1. Please refer to the SCIF chapter for details.
2. Nominal crystal cycles.
Figure 7-3. Oscillator Connection
7.7.2 32KHz Crystal Oscillator (OSC32K) Characteristics
Figure 7-3 and the equation above also applies to the 32 KHz oscillator connection. The user
must choose a crystal oscillator where the crystal load capacitance
C
L
is within the range given
in the table. The exact value of
C
L
can then be found in the crystal datasheet.
C
LEXT
2 C
L
C
i
–
( )
C
PCB
– =
Table 7-12. Crystal Oscillator Characteristics
Symbol Parameter Conditions Min Typ Max Unit
1/(t
CPMAIN
) Crystal oscillator frequency 3 16 MHz
C
L
Crystal load capacitance 6 18 pF
C
i
Internal equivalent load capacitance 2 pF
t
STARTUP
Startup time SCIF.OSCCTRL.GAIN = 2
(1)
30 000
(2)
cycles
XIN
XOUT
C
LEXT
C
LEXT
C
L
C
i
UC3L
Table 7-13. 32 KHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min Typ Max Unit
1/(t
CP32KHz
) Crystal oscillator frequency 32 768 Hz
t
ST
Startup time R
S
= 60kOhm, C
L
= 9pF 30 000
(1)
cycles
C
L
Crystal load capacitance 6 12.5 pF