66.5.1 Main Oscillator Characteristics

Table 66-17. 8 to 24 MHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min Typ Max Unit
fOSC Operating Frequency

FREQ(2) = 00, 11

FREQ = 01

FREQ = 10

8

12

16

12

16

24

MHz
Duty Cycle 40 50 60 %
tSTART Startup Time

FREQ(2) = 00, 11

FREQ = 01

FREQ = 10

18.5

10.5

6

ms
IDDON Current Consumption (on VDDIO)

@ 12 MHz

@ 24 MHz

1.2

1.7

3.5

4

mA
IDD_STDBY Standby Current 0.02 0.1 µA
CPARA Internal Parasitic Capacitance(1) From XIN to XOUT 1.4 1.6 1.8 pF
PON Drive level

FREQ = 00

FREQ = 01, 11

FREQ = 10

150

300

400

µW
Note:
  1. The values of external capacitors can be determined by using the following formula:

    CLEXT = (2 x CCRYSTAL) - CBOARD - (CPARA x 2)

    where:

    • CLEXT is the external capacitor value which must be soldered from XIN to GND and XOUT to GND
    • CCRYSTAL is crystal targeted load
    • CBOARD is the external board parasitic capacitance (from XIN to GND or XOUT to GND)
    • CPARA is the internal parasitic capacitance
  2. 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.
Figure 66-3. Main Oscillator Schematics