49.4.2 Crystal Oscillator Characteristics (XOSC32K)

The following table describes the characteristics for the oscillator when a crystal is connected between XIN32 and XOUT32.

Figure 49-5. Oscillator Connection

The user must choose a crystal oscillator where the crystal load capacitance CL is within the range given in the table. The exact value of CL can be found in the “Crystal Data Sheet”. The capacitance of the external capacitors (CLEXT) can be calculated as follows:

CLEXT=2(CL-CSTRAY-CSHUNT)

where,

CSTRAY is the capacitance of the pins, and PCB and CSHUNT is the shunt capacitance of the crystal.

Table 49-12. 32.768 kHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
Cxin32k Parasitic capacitor load - - 3.8 - pF
Cxout32k - 4.1 - pF