1. The internal wafer of the crystal oscillator is damaged or there is an internal short circuit.
2. The equivalent series resistance (ESR) of the crystal oscillator is out of tolerance.
3. The pins of the crystal oscillator are connected wrongly or there is a short circuit.
4. The frequency selection of the crystal oscillator is incorrect or the accuracy is insufficient.
5. The wrong load is selected for the crystal oscillator, including incorrect selection of the crystal oscillator load capacitance (CL) and the external matching capacitors.
6. There is a malfunction in the MCU (Microcontroller Unit).
7. The operating temperature of the crystal oscillator is out of tolerance.
8. The crystal oscillator circuit is subject to interference.
9. The excitation power is insufficient.
10. The wrong type of crystal oscillator is selected. For example, low-power consumption devices require the selection of low-power consumption crystal oscillators. Conventional crystal oscillators may not be able to be driven in the low-power consumption mode.
SIC hot-sale passive crystal oscillators
HC49S series SMD Series
DIP Series
SIC hot-sale active crystal oscillator
volume 5 * 7mm 6MHz 6M 4-pin 7050 125M 125MHz 4-pin in-line crystal
36M 36MHz 4-pin in-line crystal 12M 12MHz 4 pin inline crystal
Following: https://www.sic-chip.com/info-detail/applications-of-differential-crystal-oscillators-in-circuits