Standard Operating Conditions: VDD = 1.9V to 3.6V (unless otherwise stated) Operating Temperature: -40°C ≤ TA ≤ +85°C for Industrial Temp -40°C ≤ TA ≤ +125°C for Extended Temp
Param. No.
Symbol
Characteristics
Min.
Typ.
Max.
Units
Conditions(1)
XOSC32_1
FOSC_XOSC32
XOSC32 oscillator crystal frequency
—
32.764
—
kHz
XIN32, XOUT32 secondary oscillator
XOSC32_3
CXIN32
XOSC32 XIN32 parasitic pin capacitance
—
0.4
—
pF
0.4 pF at the SOC pins and
2.4 pF on the WBZ35x Module
2.4
XOSC32_5
CXOUT32
XOSC32 XOUT32 parasitic pin capacitance
—
0.4
—
pF
0.4 pF at the SOC pins and
2.4 pF on the WBZ35x Module
2.4
XOSC32_11
CLOAD_X32(4)
32.768 kHz crystal load capacitance
—
11
—
pF
—
XOSC32_13
ESR_X32
32.768 kHz crystal ESR
—
75
100
kΩ
—
XOSC32_15
TOSC32
TOSC32 = 1/FOSC_XOSC32
—
30.5
—
µs
See parameter XOSC32_1 for FOSC_XOSC32 value
XOSC32_17
XOSC32_ST(3)
XOSC32 crystal start-up time
—
1024
—
TOSC
Crystal stabilization time only not oscillator ready
Note:
VDDIO = AVDD = 3.3V.
The parameters are characterized but not tested in manufacturing.
This is for guidance only. A major component of crystal start-up time is based on the second party crystal MFG parasitic that is outside the scope of this specification. If this is a major concern, the customer might need to characterize this based on their design choices.
The test conditions for the crystal load capacitor calculation are as follows:
Standard PCB trace capacitance = 1.5 pF per 12.5 mm (0.5 inches) (in other words, PCB STD TRACE W = 0.175 mm, H = 36 μm, T = 113 μm)
Xtal PCB capacitance typical; therefore, ~= 2.5 pF for a tight PCB xtal layout
For CXIN and CXOUT within 4 pF of each other, assume CXTAL_EFF = ((CXIN / 2)
Note: Averaging CXIN and CXOUT will affect the final calculated CLOAD value by less than the tolerance of the capacitor selection.
Equation 1:
Assuming C1 = C2 and CXin ~= CXout, the formula can be further simplified and restated to solve for C1 and C2 by:
C1 = C2 = 13 pF (in other words, for hypothetical example crystal external load capacitors)
User C1 = C2 = 13 pF ≤ CLOAD_X32 (max.) spec
User selectable in OSC32KCTRL.STARTUP.
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