Apple Inc.
Level shifter with isolation on both input and output domains with enable from both domains

Abstract:

A system and method for efficiently handling voltage level shifting are contemplated. In various embodiments, a first level shifter receives a first isolate enable signal based on a first power supply voltage and a second isolate enable signal based on a second power supply voltage different from the first power supply voltage. A second level shifter generates the first isolate enable signal based on both the second isolate enable signal and the first power supply voltage. A circuit block generates a data signal based on the first power supply voltage. When it is determined that isolation for the first level shifter is enabled, the first level shifter generates a voltage level on an internal particular node to a particular voltage level based on the first isolate enable signal, and also prevents, using the second isolate enable signal, the data signal from setting a voltage level on the particular node.