3.1 Crystal Oscillator
The following table provides the values of the ATWINC15x0B crystal oscillator parameters.
| Parameter | Min. | Typ. | Max. | Unit |
|---|---|---|---|---|
| Crystal resonant frequency | — | 26 | — | MHz |
| Crystal equivalent series resistance | — | 50 | 150 | Ω |
| Stability – Initial offset(1) | -100 | — | 100 | ppm |
- The initial offset must be calibrated to maintain ±25 ppm in all operating conditions. This calibration is performed during final production testing.
The block diagram in the following figure (a) shows how the internal Crystal Oscillator (XO) is connected to the external crystal. The XO has 5 pF internal capacitance on each terminal XO_P and XO_N. To bypass the crystal oscillator with an external reference, an external signal capable of driving 5 pF can be applied to the XO_N terminal as shown the following figure (b).
The XO has 5 pF internal capacitance on each terminal XO_P and XO_N. This internal capacitance must be considered when calculating the external loading capacitance, c_onboard, for the XTAL.
The following table specifies the electrical and performance requirements for the external clock.
| Parameter | Min. | Typ. | Max. | Unit | Comments |
|---|---|---|---|---|---|
| Oscillator frequency | — | 26 | — | MHz | Must drive 5 pF load at desired frequency |
| Voltage swing | 0.5 | — | 1.2 | Vpp | Must be AC coupled |
| Stability – Temperature and aging | -25 | — | +25 | ppm | — |
| Phase noise | — | — | -130 | dBc/Hz | At 10 kHz offset |
| Jitter (RMS) | — | — | <1 | psec | Based on integrated phase noise spectrum from 1 kHz to 1 MHz |