The voltage threshold for triggering a Voltage-Controlled Oscillator (VCO) in clock synthesis can vary depending on the specific design and specifications of the VCO and the intended application. However, I can provide you with a general overview of how VCO triggering works.
A VCO generates an output signal, typically a waveform like a sine wave, square wave, or triangle wave, whose frequency is directly proportional to the voltage applied to its control input. To trigger or start the VCO's oscillation, the control voltage applied to the control input needs to surpass a certain threshold voltage.
This threshold voltage can vary depending on factors such as the VCO circuit's design, technology used, power supply voltage, and the desired frequency range of operation. Some VCOs might start oscillating with very low control voltages, while others might require higher control voltages to initiate oscillation.
In practical applications, the voltage threshold for triggering a VCO is often determined experimentally or by referring to the manufacturer's datasheet for the specific VCO you are using. The datasheet should provide information on the recommended control voltage range, startup behavior, and other relevant specifications.
Keep in mind that VCOs can be quite versatile and can be used in various applications beyond clock synthesis, including frequency modulation, phase-locked loops, and more. The voltage threshold for triggering will depend on the specific use case and the behavior of the VCO in that context.