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US 12,224,710 B2Granted
Low power crystal oscillator
AssigneeSTMicroelectronics International N.V.
InventorsAnand Kumar, Nitin Jain
Life of this patent
Estimating the term…
Abstract
A low power crystal oscillator circuit having a high power part and a low power part. Oscillation is initialized using the high power part. Once the crystal is under stable oscillation, the circuit switches to the low power part and continue operation for a long duration.
Claims18
A method for operating a low power crystal oscillator circuit, comprising:
- sending a startup signal of a first polarity to a startup terminal of a crystal oscillator circuit having an output terminal and a first current supply;
- driving the crystal oscillator circuit with current of a first amperage through a first current mirror having first and second current mirror transistors, the first current mirror being coupled between a high power supply and a low power supply, the crystal oscillator circuit configured to output a first voltage value at the output terminal in response to the first amperage, the startup terminal being coupled to the output terminal and to a terminal of a first startup transistor, the crystal oscillator circuit including a second current supply coupled to the low power supply and a third current mirror transistor;
- maintaining the startup signal of the first polarity at the startup terminal for a first period time;
- reversing the first polarity of the startup signal on the startup terminal to cause the first current mirror to turn off and cease to draw current;
- driving the crystal oscillator circuit with current of a second amperage through the first current mirror;
- and
- drawing current of the second amperage value from the first current supply which is J times less than the first amperage and the crystal oscillator circuit outputs voltage of a second voltage value which is K times less than the first voltage value at the output terminal.
4 more elements
A method, comprising:
- coupling a first capacitor to a crystal and a low power supply;
- coupling a first current mirror transistor to a high power supply;
- coupling a first current source to the first current mirror transistor;
- coupling the first current source to the low power supply;
- coupling a second current mirror transistor to the high power supply and the first current mirror transistor;
- coupling a first startup control transistor to the second current mirror transistor and the crystal;
- coupling a third current mirror transistor to the high power supply;
- coupling a second current source to the third current mirror transistor and to the low power supply;
- coupling a fourth current mirror transistor to the high power supply and the third current mirror transistor;
- coupling a second startup control transistor to the fourth current mirror transistor and to the crystal;
- and
- coupling a third capacitor to the third and fourth current mirror transistors and to the crystal.
9 more elements
A method, comprising:
- coupling a first capacitor to a crystal and a low power supply;
- coupling a first current mirror transistor to a high power supply;
- coupling a first current source to the first current mirror transistor and the low power supply;
- coupling a second current mirror transistor to the high power supply and the first current mirror transistor;
- coupling a first startup control transistor to the second current mirror transistor and the crystal;
- coupling a third current mirror transistor to the high power supply;
- coupling a second current source to the third current mirror transistor and the low power supply.
4 more elements
Dependencies are inferred from the claim text.