Method and apparatus for converting an analog signal into digital format
First Claim
Patent Images
1. An analog to digital converter, comprising:
- a first capacitor connected at a first terminal to an analog signal to charge the capacitor in accordance with a current voltage level of the analog signal and at a second terminal to ground;
a second capacitor; and
electronic control circuitry for alternately connecting the second capacitor between the first capacitor and a power supply to remove increments of charge from the first capacitor until the first capacitor is discharged including;
a switching circuit connected to the first terminal of the first capacitor, to ground, and to the power supply including;
a first pair of switches with one switch connected to a first terminal of the second capacitor and the other switch connected to a second terminal of the second capacitor, anda second pair of switches with one switch connected to a first terminal of the second capacitor and the other switch connected to a second terminal of the second capacitor,wherein the electronic control circuitry generates switching control signals alternately connecting the second capacitor through the first pair of switches between ground and the power supply and through the second pair of switches between the first terminal of the first capacitor and ground to remove the increments of charge from the first capacitor, andwherein a number of removed increments of charge associated with discharging the first capacitor is used to generate a digital value corresponding to the current voltage level of the analog signal.
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Abstract
A low cost, easily manufactured analog to digital converter uses MOS switching technology easily combined on an integrated circuit with other signal processing circuitry. An input capacitor stores an input analog voltage, and a pumping capacitor is switchably connected to the input capacitor to charge or discharge that input capacitor to a reference value. The number of charge or discharge events is used to generate a digital value for the input analog voltage.
41 Citations
28 Claims
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1. An analog to digital converter, comprising:
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a first capacitor connected at a first terminal to an analog signal to charge the capacitor in accordance with a current voltage level of the analog signal and at a second terminal to ground; a second capacitor; and electronic control circuitry for alternately connecting the second capacitor between the first capacitor and a power supply to remove increments of charge from the first capacitor until the first capacitor is discharged including; a switching circuit connected to the first terminal of the first capacitor, to ground, and to the power supply including; a first pair of switches with one switch connected to a first terminal of the second capacitor and the other switch connected to a second terminal of the second capacitor, and a second pair of switches with one switch connected to a first terminal of the second capacitor and the other switch connected to a second terminal of the second capacitor, wherein the electronic control circuitry generates switching control signals alternately connecting the second capacitor through the first pair of switches between ground and the power supply and through the second pair of switches between the first terminal of the first capacitor and ground to remove the increments of charge from the first capacitor, and wherein a number of removed increments of charge associated with discharging the first capacitor is used to generate a digital value corresponding to the current voltage level of the analog signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An analog to digital converter comprising:
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an input capacitor connected at a first terminal to store an analog voltage and at a second terminal to ground; control circuitry connected to the input capacitor at the first terminal; dynamic detection circuitry connected to the first terminal of the input capacitor for determining whether an input signal applied to a first input terminal of a comparator generated in response to the voltage across the input capacitor is equal to or greater than a nonzero, threshold voltage applied to a second input terminal of the comparator and for providing an output signal from the comparator to the control circuit indicating whether the input capacitor is discharged, wherein said dynamic detection circuitry is connected through a pump capacitor to a pump output signal of the control circuitry, the control circuitry alternately charging and discharging the pump capacitor using the pump output signal and discharging the input capacitor by an increment of charge after each charge and discharge cycle of the pump capacitor, until the dynamic detection circuitry indicates that the input capacitor is discharged, a total number of incremental discharges of the input capacitor being used to generate a digital value for the analog voltage. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An analog to digital converter, comprising:
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a first capacitor connected at a first terminal to an analog signal to charge the capacitor in accordance with a current voltage level of the analog signal and at a second terminal to ground; a comparator having one input terminal connected to the first terminal of the first capacitor and another input terminal connected to a reference voltage for generating; (a) a first signal when the voltage across the first capacitor is greater than the reference voltage, (b) a second signal when the voltage across the first capacitor is less than the reference voltage, and (c) a third signal when the voltage across the first capacitor is the same as the reference voltage; and electronic control circuitry for supplying increments of charge to the first capacitor when the second signal is generated until the third signal is generated and for removing increments of charge from the first capacitor when the first signal is generated until the third signal is generated, wherein the electronic control circuitry counts a number of charge increments or decrements to generate a digital value corresponding to the current voltage level of the analog signal. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A method for converting an analog signal into a digital signal comprising the steps of:
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charging a first capacitor in accordance with a current voltage level of the analog signal; comparing the voltage across the first capacitor to a reference voltage; supplying increments of charge to the first capacitor when a voltage across the capacitor is less than a reference voltage and removing increments of charge when the voltage across the first capacitor is greater than the reference voltage; and counting a number of the charge increments or decrements to generate a digital value corresponding to the current voltage level of the analog signal. - View Dependent Claims (26, 27, 28)
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Specification