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
f_CPXIN32	XIN32 clock frequency	Digital mode	-	32.768	-	kHz
DCxin	XIN32 clock duty cycle	Digital mode	-	50	-	%

Note:

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 Crystal Oscillator Characteristics also applied to the 32 kHz oscillator connection. The user must choose a crystal oscillator where the crystal load capacitance C_L is within the range given in the table. The value of C_L can be found in the crystal data sheet.

For the computation of the external capacitors (C_LEXT) 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
f_OUT	Crystal oscillator frequency		-	32768	-	Hz
t_STARTUP	Startup time	ESR_XTAL = 39.9 kΩ, C_L = 12.5 pF	-	28K	31K	cycles
C_L	Crystal load capacitance		-	-	12.5	pF
C_SHUNT	Crystal shunt capacitance		-	0.1	-
C_XIN32	Parasitic capacitor load	TQFP64/48/32 packages	-	3.1	-
C_XOUT32	Parasitic capacitor load	TQFP64/48/32 packages	-	3.3	-
I_XOSC32K	Current consumption	VDD = 3.0V, AGC off	-	1.22	2.33	μA
I_XOSC32K	Current consumption	VDD = 3.0V, AGC on⁽¹⁾	-	-	-	μA
ESR	Crystal equivalent series resistance f = 32.768 kHz  Safety Factor = 3	C_L= 12.5 pF	-	-	100	kΩ

Note:

Refer to the Errata and Data Sheet Clarification document regarding the AGC feature of XOSC32K.