Programmable highly temperature and supply independent oscillator
First Claim
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1. An oscillator circuit comprising:
- a relaxation oscillator having a current input adapted to receive a charge current, a voltage input adapted to receive a threshold voltage, and a frequency output;
a current generating circuit having an output coupled to the current input of the relaxation oscillator; and
a voltage generating circuit having an output coupled to the voltage input of the relaxation oscillator,wherein, the current generating circuit and the voltage generating circuit are configured to generate a charge current and a threshold voltage such that their temperature dependent parameters substantially cancel to yield a substantially temperature in dependent output frequency.
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Abstract
An oscillator circuit generates an output frequency that is substantially independent of power supply and temperature variations. The oscillator circuit can be implemented using conventional complementary metal-oxide-semiconductor technology. The oscillator circuit is suitable for use as an internal oscillator for generating a stable reference frequency in telecommunication receiver modules.
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Citations
15 Claims
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1. An oscillator circuit comprising:
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a relaxation oscillator having a current input adapted to receive a charge current, a voltage input adapted to receive a threshold voltage, and a frequency output; a current generating circuit having an output coupled to the current input of the relaxation oscillator; and a voltage generating circuit having an output coupled to the voltage input of the relaxation oscillator, wherein, the current generating circuit and the voltage generating circuit are configured to generate a charge current and a threshold voltage such that their temperature dependent parameters substantially cancel to yield a substantially temperature in dependent output frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An oscillator circuit comprising:
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a relaxation oscillator having a current input, a voltage input and a frequency output; a band-gap reference circuit having a temperature dependent reference current output and a substantially temperature independent reference voltage output; a current generating circuit coupled to the reference current output of the band-gap circuit, and having a field effect transistor (FET) biased in linear mode of operation, and a current output coupled to the current input of the relaxation oscillator; and a voltage generating circuit coupled to the reference voltage output of the band-gap circuit, wherein, the current generating circuit supplies to the current input of the relaxation oscillator, a charge current having a magnitude substantially proportional to a drain current of the FET operating in linear region. - View Dependent Claims (13, 14)
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15. A method of generating a reference frequency comprising the steps of:
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biasing a field effect transistor into a linear mode of operation to generate a drain current defined by a first set of temperature dependent parameters; from a band-gap reference signal, generating a stable threshold voltage defined by a second set of temperature dependent parameters; supplying a current having a magnitude defined by the drain current, to a current input of a relaxation oscillator; supplying a voltage having a level defined by the stable threshold voltage, to a threshold voltage input of the relaxation oscillator; and adjusting a level of the stable voltage so that to the second set of temperature dependent parameters substantially equal the first set of temperature dependent parameters, whereby a substantially temperature independent frequency is generated by the relaxation oscillator.
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Specification