46.13.2 External 32KHz Crystal Oscillator (XOSC32K) Characteristics
Digital Clock Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN32 pin.
Symbol | Parameter | Min. | Typ. | Max. | Units |
---|---|---|---|---|---|
fCPXIN32 | XIN32 clock frequency | 32.768 | 1000 | kHz | |
DCXIN | XIN32 clock duty cycle | 40 | 50 | 60 | % |
- These values are based on simulation. They are not covered by production test limits or characterization.
Crystal Oscillator Characteristics
The following section describes the characteristics for the oscillator when a crystal is connected between XIN32 and XOUT32 pins.
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 - CPARA - CPCB - CSHUNT)
Where:
- CPARA is the internal load capacitor parasitic between XIN and XOUT ( CPARA = (CXIN32K CXOUT32K)/(CXIN32K + CXOUT32K) )
- CPCB is the capacitance of the PCB
- CSHUNT is the shunt capacity of the crystal.
Symbol | Parameter | Conditions | Min. | Typ. | Max. | Units |
---|---|---|---|---|---|---|
FOUT | Crystal oscillator frequency | - | - | 32.768 | - | kHz |
CL(1) | Crystal load capacitance | - | 7 | - | 9 | pF |
CSHUNT(1) | Crystal shunt capacitance | - | 0.6 | - | 2 | pF |
CM(1) | Motional capacitance | - | 0.6 | - | 3 | fF |
ESR(2) | Crystal Equivalent Series Resistance - SF=3 |
f=32.768kHz, |
- | - | 70 | kΩ |
CXIN32k(2) | Parasitic load capacitor | - | - | 3.2 | - | pF |
CXOUT32k(2) | - | - | 3.4 | - | ||
tSTARTUP(2) | Startup time |
f=32.768kHz, |
- | 10 | 43 | KCycles |
Pon(1) | Drive Level | - | - | - | 0.1 | µW |
- These values are based on simulation. They are not covered by production test limits or characterization.
- These values are based on characterization. They are not covered in test limits in production.
Symbol | Parameter | Conditions | Ta | Min. | Typ. | Max. | Units |
---|---|---|---|---|---|---|---|
IDD | Current consumption | VCC=3.3V | Max 85°C Typ 25°C |
- | 309 | 606 | nA |
- These values are based on characterization. They are not covered in test limits in production.