45.12.2.2 Crystal Oscillator Characteristics

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

Figure 45-6. 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 then be computed 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 45-50. 32.768 kHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
fOUT (1) Crystal oscillator frequency - 32768 - Hz
CL (1) Crystal load capacitance - - 12.5 pF
CSHUNT (1) Crystal shunt capacitance - - 1.75 pF
Cm (1) Motional capacitance - 1.25 - fF
ESR Crystal Equivalent Series Resistance - SF = 3 F = 32.768 kHz, CL=12.5 pF - - 79 kΩ
Cxin32k Parasitic capacitor load - 2.9 - pF
Cxout32k - 3.2 - pF
Tstart Startup time F = 32.768 kHz, CL=12.5 pF - 16 24 Kcycles
  1. These are based on simulation. These values are not covered by test or characterization
Table 45-51. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption VDD = 5.0V

Max 85°C

Typ 25°C

 1528 1720 nA
  1. These are based on characterization.