41.12.2.2 XOSC32K Characteristics

Figure 41-6 and the equation in XOSC Characteristics also apply 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 data sheet.

Table 41-40. 32 kHz Crystal Oscillator Characteristics
ParameterConditionsSymbolMin.Typ.Max.Unit
Crystal oscillator frequencyfOUT-32768-Hz
Start-up time

ESRXTAL = 39.9 kΩ,

CL = 12.5 pF

tSTARTUP-28K30Kcycles
Crystal load capacitanceCL--12.5pF
Crystal shunt capacitanceCSHUNT-0.1-pF
Parasitic capacitor loadCXIN32-3.2-pF
Parasitic capacitor loadCXOUT32-3.7-pF
Current consumptionIXOSC32K-1.222.2μA

Crystal equivalent series resistance

f = 32.768 kHz


Safety Factor = 3

CL=12.5pFESR--100kΩ