The Features of Silicon Oscillator

For the requirement of most MCU clock, silicon oscillator is a simple and effective solving plan. Be different with crystal and ceramic oscillator. Silicon timer is not sensitive to the vibration, shock and EMI. In addition, silicon oscillator does not need to be elaborately matched with the timer device or strict PCB wiring.

In the practical application, besides some environmental factors, the choosing standard of clock source usually according to the following four conditions: precision, supply voltage, size and noise. Precision demand is commonly decided by communication standard adopted by particular application, for example, high speed USB need ±0.25% total clock precision. Systems which do not need the external communication need only 5%, 10% even 20% clock source precision to work.

The comparison of silicon oscillator and crystal or ceramic oscillator

The supply voltage of MCU clock typical range is from 1V to 5.5V, while the silicon oscillator supply voltage range is from 2.4V to 5.5V.

Clock noise can be affected by many factors, including amplifier noise, power supply noise, PCB wiring and the inherent noise suppression of oscillating components. The Q value of crystal is very high, thus, generally speaking, it produces the lowest noise, especially suit for systems needed low base band noise, such as voice frequency CODEC.

However, silicon oscillator occupied the smallest space, and it dose not need to add timer device. For most silicon oscillator, the external components it need is a power bypass capacitor.

Most crystal and ceramic oscillator are used in Pierce oscillator. Among them, crystal or resonator are used in the feedback of inverting amplifier as the tuned cell. In order to stabilize the circuit, we need to add capacitors and resistors to have phase shift and gain control. In addition, we need to use resistor to provide certain damp to prevent over-drive causing crystal or oscillator permanent damage.

Silicon oscillator, the totally integrated oscillating device, is the simplest clock source. These equipments can produce assigned frequency square wave, which directly sent to the clock input of MCU. Silicon oscillator does not rely on the mechanical resonate characteristics but base on an inner RC time constant to get oscillator frequency. This kind of design makes silicon devices have no sensitive to external mechanism.