Ramp generator circuit
First Claim
Patent Images
1. A ramp generator circuit, comprising:
- a capacitor;
a current source circuit configured to generate a source current having a variable magnitude;
a first switch configured to selectively apply the source current to the capacitor and generate a ramp signal at said capacitor; and
a trimming circuit configured to measure a time taken for the ramp signal to reach a threshold, compare the measured time to a reference time and adjust the variable magnitude of the source current in response to a result of the comparison.
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Abstract
An oscillator circuit selectively charges and discharges a capacitor with currents having variable magnitudes. A trimming circuit functions to measure a half period of the oscillator signal. The measured half period is compared to a reference period to generate an error signal. The variable magnitudes of one or the other or both of the current for sourcing or sinking at the capacitor are adjusted in response to the error signal.
19 Citations
21 Claims
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1. A ramp generator circuit, comprising:
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a capacitor; a current source circuit configured to generate a source current having a variable magnitude; a first switch configured to selectively apply the source current to the capacitor and generate a ramp signal at said capacitor; and a trimming circuit configured to measure a time taken for the ramp signal to reach a threshold, compare the measured time to a reference time and adjust the variable magnitude of the source current in response to a result of the comparison. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An oscillator circuit, comprising:
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a capacitor; a current source circuit configured to generate a source current having a variable magnitude; a first switch configured to selectively apply the source current to the capacitor and generate a positive ramp of an oscillator signal at said capacitor; a current sink circuit configured to generate a sink current having a variable magnitude; a second switch configured to selectively apply the sink current to the capacitor and generate a negative ramp of the oscillator signal at said capacitor; a switch control circuit configured to alternately actuate the first and second switches; a trimming circuit configured to measure a half period of the oscillator signal, compare the measured half period to a reference period and adjust the variable magnitude of the source current and sink current in response to a result of the comparison. - View Dependent Claims (14, 15, 16, 17)
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18. A method of generating a ramp signal, comprising:
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applying a source current having a variable magnitude to a capacitor to generate a ramp signal at said capacitor; measuring a time taken for the ramp signal to reach a threshold; comparing the measured time to a reference time; and adjusting the variable magnitude of the source current in response to a result of the comparison. - View Dependent Claims (19, 20, 21)
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Specification