1. Field of the Invention
The invention relates to a system on chip (SOC), and more particularly, to isolation circuits in a level shifter.
2. Description of the Related Art
FIG. 1 shows a conventional system on chip (SOC) utilizing a level shifter 100. Signals passed between the first voltage domain 110 and the second voltage domain 120 are converted by the level shifter 100 to adapt to the corresponding voltage domain. There are various known techniques for implementing level shifter 100, thus, a detailed description thereof is omitted. In an 500, however, the first voltage domain 110 or second voltage domain 120 may be selectively or occasionally powered down, switching the corresponding terminal on level shifter 100 to a floating state. For example, when the first terminal V1 is floating, the level shifter 100 may output an indeterminable signal to the second terminal V2. If the second voltage domain 120 receives the indeterminable signal, unexpected application errors may occur.