Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 1061

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

When choosing a crystal for the 32768 Hz Slow Clock Oscillator or for the 3–20 MHz Oscillator, several parameters must 
be taken into account. Important parameters between crystal and SAM4S specifications are as follows:



Load Capacitance



C

crystal

 is the equivalent capacitor value the oscillator must “show” to the crystal in order to oscillate at the 

target frequency. The crystal must be chosen according to the internal load capacitance (C

L

) of the on-chip 

oscillator. Any mismatch in the load capacitance will result in a frequency drift.



Drive Level



Crystal drive level 

≥ Oscillator drive level. Having a crystal drive level number lower than the oscillator 

specification may damage the crystal.



Equivalent Series Resistor (ESR)



Crystal ESR 

≤ Oscillator ESR Max. Having a crystal with ESR value higher than the oscillator may cause the 

oscillator to not start.



Shunt Capacitance



Max. crystal Shunt Capacitance 

≤ Oscillator Shunt Capacitance (

C

SHUNT

). 

Having a crystal with ESR value 

higher than the oscillator may cause the oscillator to not start.

SAM4S oscillators are low-power oscillators requiring particular attention when designing PCB systems.