39.8.2.2 Crystal Oscillator Characteristics

Figure 37-6 and the equation in 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 data sheet.

Table 39-35. 32kHz Crystal Oscillator Characteristics (Device Variant A)
SymbolParameterConditionsMin.Typ.Max.Units
fOUTCrystal oscillator frequency-32768-Hz
tSTARTUPStartup timeESRXTAL = 39.9 kΩ, CL = 12.5 pF-28K31Kcycles
CLCrystal load capacitance--12.5pF
CSHUNTCrystal shunt capacitance-0.1-
CXIN32Parasitic capacitor loadTQFP64/48/32 packages-3.1-
CXOUT32Parasitic capacitor load-3.3-
IXOSC32KCurrent consumption-1.222.44µA
ESRCrystal equivalent series resistance f=32.768kHz
, Safety Factor = 3CL=12.5pF--141kΩ
Table 39-36. 32kHz Crystal Oscillator Characteristics (Device Variant B, C, D and L)
SymbolParameterConditionsMin.Typ.Max.Units
fOUTCrystal oscillator frequency-32768-Hz
tSTARTUPStartup timeESRXTAL = 39.9 kΩ, CL = 12.5 pF-28K30Kcycles
CLCrystal load capacitance--12.5pF
CSHUNTCrystal shunt capacitance-0.1-
CXIN32Parasitic capacitor loadTQFP64/48/32 packages-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