| 摘要 |
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.
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