38.8.2.2 Crystal Oscillator Characteristics

Figure 38-4 and the equation in Crystal Oscillator Characteristics also applies to the 32 kHz 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 datasheet.

Table 38-24. 32kHz Crystal Oscillator Characteristics
SymbolParameterConditionsMin.Typ.Max.Units
fOUTCrystal oscillator frequencyI-32768-Hz
tSTARTUPStartup timeESRXTAL = 39.9 kΩ, CL = 12.5 pF-28K30Kcycles
CLCrystal load capacitanceI--12.5pF
CSHUNTCrystal shunt capacitanceI-0.1-
CXIN32Parasitic capacitor load -3.2-
CXOUT32Parasitic capacitor load-3.7-
IXOSC32KCurrent consumption-1.222.2μA
ESRCrystal equivalent series resistance f=32.768kHz
Safety Factor = 3CL=12.5pF--100kΩ