Method for detecting minimum operational frequency

A method of detecting a minimum operational frequency, comprising:

• generating a signal that becomes an oscillating signal at a first predetermined frequency, comprising:
• generating a first oscillating signal by increasing frequency of the generated signal;
• and
• generating a second oscillating signal by filtering the first oscillating signal to reduce noise;
• and
• generating a logic signal to provide a level transition when a frequency of the first oscillating signal reaches a second predetermined frequency corresponding to the minimum operational frequency, comprising:
• providing a transistor that is activated when the first oscillating signal reaches the second predetermined frequency;
• and
• generating the logic signal when the transistor is activated.

A method of detecting a minimum operational frequency, comprising:

• generating a signal that becomes an oscillating signal at a first predetermined frequency, comprising:
• generating a first oscillating signal by increasing frequency of the generated signal;
• and
• generating a second oscillating signal by filtering the first oscillating signal to reduce noise;
• and
• generating a logic signal to provide a level transition when a frequency of the first oscillating signal reaches a second predetermined frequency corresponding to the minimum operational frequency, comprising:
• providing a capacitor;
• storing charges in the capacitor until the first oscillating signal reaches the second predetermined frequency and discharging the capacitor when the first oscillating signal reaches the second predetermined frequency;
• and
• outputting the logic signal when the capacitor discharges.

A method of detecting a minimum operational frequency, comprising:

• generating a signal that becomes an oscillating signal at a first predetermined frequency;
• and
• generating a logic signal to provide a level transition when a frequency of the oscillating signal reaches a second predetermined frequency corresponding to the minimum operational frequency, comprising:
• providing a transistor that is activated at the second predetermined frequency;
• providing a capacitor;
• storing charges in the capacitor when the oscillating signal is below the second predetermined frequency;
• discharging the capacitor when the transistor is activated by the oscillating signal;
• and
• outputting the logic signal when the capacitor discharges.