67.6.1 Main Oscillator Characteristics

Table 67-18. 8 to 24 MHz Crystal Oscillator Characteristics
Symbol	Parameter	Conditions	Min	Typ	Max	Unit
f_OSC	Operating Frequency	FREQ⁽²⁾ = 00, 11 FREQ = 01 FREQ = 10	8 12 16	–	12 16 24	MHz
–	Duty Cycle	–	40	50	60	%
t_START	Startup Time	FREQ⁽²⁾ = 00, 11 FREQ = 01 FREQ = 10	–	–	18.5 10.5 6	ms
I_DDON	Current Consumption (on VDDIO)	@ 12 MHz @ 24 MHz	–	1.2 1.7	3.5 4	mA
I_{DD_STDBY}	Standby Current	–	–	0.02	0.1	µA
C_PARA	Internal Parasitic Capacitance⁽¹⁾	From XIN to XOUT	1.4	1.6	1.8	pF
P_ON	Drive level	FREQ = 00 FREQ = 01, 11 FREQ = 10	–	–	150 300 400	µW

Note:

The values of external capacitors can be determined by using the following formula:
C_LEXT = (2 x C_CRYSTAL) - C_BOARD - (C_PARA x 2)
where:
- C_LEXT is the external capacitor value which must be soldered from XIN to GND and XOUT to GND
- C_CRYSTAL is crystal targeted load
- C_BOARD is the external board parasitic capacitance (from XIN to GND or XOUT to GND)
- C_PARA is the internal parasitic capacitance
The SFR_UTMICKTRIM.FREQ field defines the input frequency for the UTMI and the main oscillator. It is important to select the correct FREQ value because this has a direct influence on USB frequency.