48.6.2. Crystal Oscillator
Figure 48-8. Crystal Oscillator Schematic
XOUT
XIN
15pF
15pF
The crystal should be located as close to the device as possible. Long signal lines may cause too high
load to operate the crystal, and cause crosstalk to other parts of the system.
Table 48-5. Crystal Oscillator Checklist
Signal Name
Recommended Pin Connection
Description
XIN
Load capacitor 15pF
(1)(2)
External crystal between 0.4 to 32MHz
XOUT
Load capacitor 15pF
(1)(2)
1. These values are only given as a typical example.
2. The capacitors should be placed close to the device for each supply pin pair in the signal group.
48.6.3. External Real Time Oscillator
The low frequency crystal oscillator is optimized for use with a 32.768kHz watch crystal. When selecting
crystals, load capacitance and the crystal’s Equivalent Series Resistance (ESR) must be taken into
consideration. Both values are specified by the crystal vendor.
SAM L22 oscillator is optimized for very low power consumption, hence close attention should be made
when selecting crystals.
The typical parasitic load capacitance values are available in the Electrical Characteristics section. This
capacitance and PCB capacitance can allow using a crystal inferior to 12.5pF load capacitance without
external capacitors as shown in
Figure 48-9. External Real Time Oscillator without Load Capacitor
XOUT32
XIN32
32.768kHz
To improve accuracy and Safety Factor, the crystal datasheet can recommend adding external capacitors
as shown in
To find suitable load capacitance for a 32.768kHz crystal, consult the crystal datasheet.
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
1199