Dual-Supply Level Shifter Circuit for Missing High-Voltage Rails
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Solution Overview
Problem
Conventional level shifter circuits fail to operate properly when the higher power supply voltage is diminished or absent, leading to a 'floating node' that disrupts digital information flow between domains with different power supply voltage levels, causing operational issues in integrated circuits.
Innovation Solution
A dual supply level shifter circuit is introduced, comprising a supply switching circuit and multiple level shifter circuits using CMOS transistors, which ensures continuous operation even without the upper power supply voltage by switching between power supply voltages Vdd and Vdda, preventing a floating node and consuming no quiescent current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional level shifter circuit is used to translate signals between domains with different power supply voltage levels, then signal translation is achieved, but the circuit fails to operate properly when the higher power supply voltage is diminished or absent, creating a floating node that disrupts digital information flow
Solution Approach 1:
The level shifter circuit dynamically adapts its operation based on the presence and voltage levels of VDDA and VDD power supplies. The circuit transitions between different operational modes: when VDDA is present it operates in high-voltage mode for optimal signal translation, and when VDDA is absent or at lower voltage it automatically switches to alternative operational paths using only VDD, ensuring continuous reliable operation without floating nodes under varying power supply conditions
Solution Approach 2:
The circuit changes its operational parameters based on power supply conditions. By monitoring the presence and voltage levels of VDDA and VDD, the circuit adjusts its internal transistor biasing and signal translation characteristics accordingly. This parameter adaptation allows the circuit to maintain proper signal levels and avoid floating nodes whether operating with dual power supplies or single power supply, thereby improving reliability across different power scenarios
2Reliability
If separate level shifter circuits are used for different power supply voltage domains, then proper signal translation is achieved, but the cost and space requirements increase
Solution Approach 1:
The level shifter circuit is designed with multi-functionality to handle multiple power supply configurations. A single circuit instance can operate with both VDDA and VDD present, with only VDD present, or with varying voltage levels, eliminating the need for separate dedicated level shifters for different voltage domains. This universal design reduces device complexity and space requirements while maintaining accurate signal translation across all operating conditions
Data Source
AI summary
A dual supply level shifter circuit includes a switching circuit and a set of level shifter circuits coupled to the switching circuit. The switching circuit includes a first set of coupled transistors, wherein the supply switching circuit is coupled to a first supply source that is configured to provide a first power supply voltage and is coupled to a second supply source that is configured to provide a second power supply voltage. The set of level shifter circuits includes a second set of coupled transistors, wherein the set of level shifter circuits is configured to receive a voltage input signal at an input node from a first circuit and to supply to an output node of the dual supply level shifter circuit an output signal having a value that is a highest voltage value between the first power supply voltage and the second power supply voltage.