A/D CONVERTER USING ISOLATION SWITCHES
First Claim
1. An analog-to-digital converter comprising:
- a plurality of capacitors;
a first sampling switch connected to selectively couple a first capacitor in the plurality of capacitors to an input voltage signal during a sampling operation;
a plurality of conversion switches connected to selectively apply a plurality of reference voltage potentials to individual capacitors within the plurality of capacitors during a conversion operation;
a first isolation switch coupled between the first capacitor and a first conversion switch in the plurality of conversion switches; and
a controller configured to control the first isolation switch such that the first conversion switch is substantially isolated from the input voltage signal during the sampling operation, the controller further configured to selectively control the plurality of conversion switches during the conversion operation to derive a digital code corresponding to a sampled value of the input voltage signal.
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Accused Products
Abstract
In an A/D converter, isolation switches are used between the capacitors and the conversion switches. The conversion switches are those switches used to selectively couple the plates of the binary weighted capacitors to either Vref or 0 volts during the A/D conversion process. During sampling of the input voltage signal, the isolation switches are opened to isolate the conversion switches from the wide range of possible input voltages at the bottom plates of the capacitors. Therefore, the voltage across the conversion switches is substantially limited to Vref. Hence, the conversion switches can be very fast low voltage switches. After sampling of the input voltage, when the sampled input voltage is locked in, the conversion switches operate normally to selectively connect the capacitor plates to either Vref or 0 volts for successively approximating the input voltage, whereby a digital code representing the sampled input voltage is generated.
17 Citations
20 Claims
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1. An analog-to-digital converter comprising:
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a plurality of capacitors; a first sampling switch connected to selectively couple a first capacitor in the plurality of capacitors to an input voltage signal during a sampling operation; a plurality of conversion switches connected to selectively apply a plurality of reference voltage potentials to individual capacitors within the plurality of capacitors during a conversion operation; a first isolation switch coupled between the first capacitor and a first conversion switch in the plurality of conversion switches; and a controller configured to control the first isolation switch such that the first conversion switch is substantially isolated from the input voltage signal during the sampling operation, the controller further configured to selectively control the plurality of conversion switches during the conversion operation to derive a digital code corresponding to a sampled value of the input voltage signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A signal-processing circuit receiving an analog input signal within a full-scale input voltage range characterized by a lower input voltage limit and an upper input voltage limit, the signal-processing circuit comprising:
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a first circuit that processes signals only within a first voltage range that is substantially less wide than the full-scale input voltage range; a capacitor having a first capacitor terminal and a second capacitor terminal; an input switch selectively coupling the analog input signal to the first capacitor terminal; and an isolation switch selectively coupling the first circuit to the first capacitor terminal, wherein the input switch is substantially conductive and the isolation switch is substantially non-conductive during a sampling operation, and the isolation switch is substantially conductive and the input switch is substantially non-conductive during a signal-processing operation. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification