Patent ID: 8643425
Filing Date: 2014-02-04
Classification: H03K

Abstract:
1. A method for operating a level shifter circuit to maintain forward supply voltage levels in predefined ranges, the method comprising: sensing a core supply voltage level; comparing the sensed core supply voltage level with a predefined core supply voltage level needed to ensure voltage level shifting at an output of the level shifter circuit; maintaining one or more input nodes and one or more internal nodes of the level shifter circuit at a predetermined voltage level when the sensed core supply voltage level is below the predefined core supply voltage level; operating the level shifter circuit using a transistor pair connected as a differential amplifier; and protecting the transistor pair with a pair of protection transistors, wherein the protection transistors receive an input from at least one of the one or more input nodes, and wherein gates of the protection transistor pair are biased within a predefined voltage difference from the core supply voltage level.