Data Sheet

970
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
36.11 Oscillators Characteristics
36.11.1 Crystal Oscillator (XOSC) Characteristics
36.11.1.1 Digital Clock Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN.
Table 36-44. Digital Clock Characteristics
36.11.1.2 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 36-6. 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
STRAY
is the capacitance of the pins and PCB, C
SHUNT
is the shunt capacitance of the crystal.
Symbol Parameter Conditions Min. Typ. Max. Units
f
CPXIN
XIN clock frequency
I
- - 32 MHz
Table 36-45. Crystal Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
f
OUT
Crystal oscillator frequency
I
0.4 - 32 MHz
ESR
Crystal Equivalent Series
Resistance
Safety Factor = 3
The AGC doesn’t have any
noticeable impact on these
measurements.
f = 0.455MHz, C
L
= 100pF
XOSC.GAIN = 0
- - 5.6K
Ω
f = 2MHz, C
L
= 20pF
XOSC.GAIN = 0
- - 416
f = 4MHz, C
L
= 20pF
XOSC.GAIN = 1
- - 243
f = 8MHz, C
L
= 20pF
XOSC.GAIN = 2
- - 138
f = 16MHz, C
L
= 20pF
XOSC.GAIN = 3
- - 66
f = 32MHz, C
L
= 18pF
XOSC.GAIN = 4
- - 56
C
XIN
Parasitic capacitor load
I
- 5.9 - pF
C
XOUT
Parasitic capacitor load - 3.2 - pF
C
LEXT
2C
L
C
STRAY
C
SHUNT
––()=