67.6.1 Main Oscillator Characteristics

Table 67-18. 8 to 24 MHz Crystal Oscillator Characteristics
SymbolParameterConditionsMinTypMaxUnit
fOSCOperating Frequency

FREQ(2) = 00, 11

FREQ = 01

FREQ = 10

8

12

16

12

16

24

MHz
Duty Cycle405060%
tSTARTStartup Time

FREQ(2) = 00, 11

FREQ = 01

FREQ = 10

18.5

10.5

6

ms
IDDONCurrent Consumption (on VDDIO)

@ 12 MHz

@ 24 MHz

1.2

1.7

3.5

4

mA
IDD_STDBYStandby Current0.020.1µA
CPARAInternal Parasitic Capacitance(1)From XIN to XOUT1.41.61.8pF
PONDrive 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 67-3. Main Oscillator Schematics