Control circuit and method for a crystal oscillator using a timer
AssigneeSTMicroelectronics S.r.l.
InventorRong Yin
Life of this patent
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Abstract
A circuit and method are disclosed for controlling current dissipated by an oscillator circuit. The circuit includes a current source adapted to source current to or sink current from the oscillator circuit. A control circuit is adapted to count a predetermined period of time following the occurrence of an event, such as completion of a power-up operation. An output of the control circuit, having a value indicative of whether the predetermined period of time has elapsed, is coupled to a control input of the current source. In this way, the output of the control circuit sets a current level sourced to or sunk from the oscillator circuit by the current source.
Claims24
An oscillator circuit, comprising:
- a crystal oscillator circuit adapted to oscillate at approximately a predetermined frequency;
- and
- a control circuit coupled to the crystal oscillator circuit for controlling a current level at which the crystal oscillator circuit operates, the control circuit selectively switching the current level from a first current level to a second current level different from the first current level in response to a timer circuit which measures a predetermined period of time following an occurrence of an event.
A method for generating an oscillating signal, comprising:
- generating, at a first current level, an output signal to oscillate between at least two voltage levels at around a predetermined frequency, each voltage level corresponding to a distinct logic state;
- receiving an input signal having a value indicative an occurrence of an event;
- counting at least a predetermined period of time following the input signal having the value indicative of the occurrence of the event, and
- generating, at a second current level different from the first current level, the output signal to oscillate at around the predetermined frequency.
A system, comprising:
- circuitry responsive to at least one signal that oscillates at approximately a predetermined frequency;
- and
- oscillator circuitry adapted to generate the at least one signal at a first current and, subsequent to approximately a predetermined period of time after an occurrence of an event as measured by a timer circuit, at a second current level different from the first current level.
Dependencies are inferred from the claim text.