34.12.2 External 32 kHz Crystal Oscillator (XOSC32K) Characteristics

Digital Clock Characteristics

The following table describes the characteristics for the oscillator when a digital clock is applied on the XIN32 pin.

Table 34-35. Digital Clock Characteristics (1)
Symbol Parameter Conditions Min. Typ. Max. Units
fCPXIN32 XIN32 clock frequency Digital mode - 32.768 - kHz
DCxin XIN32 clock duty cycle Digital mode - 50 - %
Note:
  1. These values are based on simulation. These values are not covered by test or characterization.

Crystal Oscillator Characteristics

Figure 32-6 and the equation in 32.12.1.2 Crystal Oscillator Characteristics also applied 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 value of CL can be found in the crystal data sheet.

For the computation of the external capacitors (CLEXT) value, refer to the logic detailed in XOSC Crystal Oscillator Characteristics.

Table 34-36. 32 kHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
fOUT Crystal oscillator frequency - 32768 - Hz
tSTARTUP Startup time ESRXTAL = 39.9  kΩ, CL = 12.5  pF - 28K 31K cycles
CL Crystal load capacitance - - 12.5 pF
CSHUNT Crystal shunt capacitance - 0.1 -
CXIN32 Parasitic capacitor load TQFP64/48/32 packages - 3.1 -
CXOUT32 Parasitic capacitor load - 3.3 -
IXOSC32K Current consumption VDD = 3.0V, AGC off - 1.22 2.33 μA
VDD = 3.0V, AGC on(1) - - -
ESR Crystal equivalent series resistance f = 32.768 kHz
 Safety Factor = 3 CL= 12.5 pF - - 100 kΩ
Note:
  1. Refer to the Errata and Data Sheet Clarification document regarding the AGC feature of XOSC32K.