Auto-Isolation Level Shifter for Floating Input Signals
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Solution Overview
Problem
Conventional system on chip (SOC) level shifters can output indeterminable signals when a voltage domain is powered down, leading to unexpected application errors due to floating terminals.
Innovation Solution
The implementation of isolation circuits, such as latch or pulling circuits, coupled to the output of level shifters, which automatically output a substitution signal with a predetermined voltage level when the input is floating, preventing indeterminable signals from being passed to other voltage domains without the need for a control input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a voltage domain is powered down to save energy, then energy consumption is reduced, but the terminal becomes floating and outputs indeterminable signals causing errors
Solution Approach 1:
The patent introduces an isolation circuit as an intermediary component between the level shifter and the second voltage domain. This isolation circuit detects when the first voltage domain is powered down and automatically outputs a predetermined substitution signal instead of passing through the indeterminable floating signal, thereby preventing errors while allowing power savings
2Device complexity
If the level shifter outputs signals directly without isolation, then device complexity is reduced, but floating terminals produce indeterminable signals that cause application errors
Solution Approach 1:
The isolation circuit is designed to automatically detect the floating state of the level shifter output and self-regulate by outputting a predetermined substitution signal without requiring external control inputs. This self-service mechanism maintains signal stability while adding minimal complexity to the overall system
Data Source
AI summary
The disclosure relates to a voltage converter, converting a first signal of a first voltage to output a second signal of a second voltage. A level shifter receives the first signal to generate the second signal. An isolation circuit is coupled to the output of the level shifter, passing the second signal out. When the input of voltage converter is floated, the isolation circuit stops passing the second signal as the output, instead, the isolation circuit outputs a substitution signal having a predetermined voltage level irrelevant to the input of the level shifter.