US Patent 7956655 Output pad system and pad driving circuit thereof

A pad driving circuit includes an output control circuit, a voltage pump circuit, a first buffer series, and a second buffer series. The output control circuit controls whether a pad circuit can pass an input signal, in which the output control circuit enables the pad circuit to output the input signal when an enable signal is asserted. The voltage pump circuit generates a negative supply voltage having voltage less than a zero volt. The first buffer series, electrically connected between the output control circuit and the pad circuit, drives the pad circuit with a positive supply voltage and the negative supply voltage from the voltage pump circuit. The second buffer series drives the pad circuit with a ground voltage and the positive supply voltage.