Patent ID: 8373485

Claim:
A voltage level shifting apparatus, comprising: a cross-coupled transistor pair, coupled to an operational voltage; a plurality of transistor pairs, one of which being coupled to the cross-coupled transistor pair, the gates of transistors of each of the transistor pairs being coupled to each other, and the transistor pairs being controlled by a plurality of reference voltages; a first diode string; a second diode string, the first diode string and the second diode string coupled between two of the transistor pairs, and each of the first diode string and the second diode string having at least a diode; an input transistor pair, coupled between a ground voltage and the transistor pairs in serial, gates of transistors of the input transistor pair receiving a first input voltage and a second input voltage, and the first input voltage and a second input voltage being complementary signals; a first low-voltage-mode transistor string, having a plurality of first low-voltage-mode transistors coupled between the cross-coupled transistor pair and the ground voltage, the first low-voltage-mode transistors are respectively controlled by a third reference voltage of the reference voltages, a mode selection signal and the first input voltage; a second low-voltage-mode transistor string, having a plurality of second low-voltage-mode transistors coupled between the cross-coupled transistor pair and the ground voltage, the second low-voltage-mode transistors are respectively controlled by the third reference voltage, the mode selection signal and the second input voltage; and an operational voltage detector, coupled to the operational voltage, for generating the mode selection signal according to a voltage level of the operational voltage; wherein the cross-coupled transistor pair has a first output end and a second output end, and the cross-coupled transistor pair shifts the first input voltage and the second input voltage according to the operational voltage to generate and output a first output voltage and a second output voltage through the first output end and the second output end respectively.