Patent ID: 7528628

Claim:
A voltage converter, converting a first signal of a first voltage to output a second signal of a second voltage, comprising: a level shifter, receiving the first signal to generate the second signal; and an isolation circuit, coupled to an output of the level shifter, wherein when an input of the level shifter is floating, the isolation circuit outputs a substitution signal as an output signal of the level shifter, and the output signal is irrelevant to the floating input of level shifter; wherein the level shifter further comprises: an output terminal and a complementary output terminal, wherein the output of the level shifter is the output terminal; and a first inverter and a second inverter serially coupled to the output terminal for outputting the second signal; the isolation circuit is an inverter with an input terminal coupled to an output of the first inverter, feeding the output of the first inverter back to an input of the first inverter; wherein: when the input of level shifter is not floating, the output terminal is dominated by the level shifter to output the second signal via the first inverter and second inverter; and when the input of level shifter is floating, the inverter with the first inverter form a latch circuit to continue outputting a previous state of the second signal as the substitution signal.