Patent ID: 7940091

Claim:
An apparatus for sampling an input voltage, comprising: a voltage sampling circuit coupled to receive the input voltage up to or greater than a supply voltage and configured to produce a sampled input voltage at an output terminal; a voltage charging circuit coupled to the voltage sampling circuit via a first connection, to a power supply voltage, and to first and second pulse signals, producing a first charged voltage at a first charged voltage output terminal and a second charged voltage at a second charged voltage output terminal; and a control circuit coupled to the voltage sampling circuit, to the voltage charging circuit, and configured to receive the power supply voltage, ground, and third and fourth pulse signals, wherein the first and third pulse signals are non-overlapping with the second and fourth pulse signals, respectively, each high pulse of the first pulse signal is within a corresponding high pulse of the third pulse signal, with a rising edge of the high pulse of the first pulse signal delayed with respect to that of the high pulse of the third pulse signal and a falling edge of the high pulse of the third pulse signal delayed with respect to that of the high pulse of the first pulse signal, each high pulse of the second pulse is within a corresponding high pulse of the fourth pulse signal, with a rising edge of the high pulse of the second signal is delayed with respect to that of the high pulse of the fourth pulse signal and a falling edge of the high pulse of the fourth pulse signal delayed with respect to that of the high pulse of the second pulse signal; wherein the voltage charging circuit comprises: a first voltage charging circuit coupled to the voltage sampling device via the first connection and producing the first charged voltage at the first charged voltage output terminal; a second voltage charging circuit coupled to the power supply and the first and second pulse signals, and producing the second charged voltage at the second charged voltage output terminal; and a voltage charging enabling circuit coupled to the first voltage charging circuit and the second voltage charging circuit, the voltage sampling device via the first connection, and to receive the power supply voltage.