Multi-Stage Voltage Level Shifters Within Low-Voltage SOA
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Solution Overview
Problem
Existing voltage level shifters in integrated circuits face challenges in achieving performance improvement, size scaling, and reducing power consumption without violating the safe operating area (SOA) of low voltage transistors, leading to undesirable trade-offs in circuit complexity and power consumption.
Innovation Solution
A single-stage or multi-stage voltage level shifter design using symmetric low voltage transistors connected to multiple positive voltage rails, where each stage receives input voltage pulses and outputs multiple output pulses, ensuring operation within the safe operating area by maintaining symmetric transistor configurations and voltage ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low voltage transistors are used to reduce power consumption, then power consumption is reduced, but the transistors operate outside the safe operating area
Solution Approach 1:
The voltage level shifter is divided into multiple stages, with each stage handling a portion of the voltage translation task. This segmentation allows low voltage transistors to operate within their safe operating area by distributing the voltage stress across multiple devices rather than placing excessive stress on a single transistor.
Solution Approach 2:
Intermediate voltage nodes are introduced between the input and final output, creating stepped voltage transitions. These intermediary nodes allow low voltage transistors to handle smaller voltage differences, keeping them within their safe operating area while still achieving the overall voltage level shifting function.
2Reliability
If asymmetric high voltage transistors are used to avoid operation outside SOA, then safe operating area is maintained, but circuit complexity increases
Solution Approach 1:
The patent intentionally introduces asymmetry in the voltage rail configuration (different positive voltage levels) to enable the use of symmetric low voltage transistors. This asymmetric voltage architecture allows all transistors to operate symmetrically within their safe operating area, avoiding the need for asymmetric high voltage transistor designs.
3Reliability
If discrete biasing circuits are added to maintain SOA, then safe operating area is maintained, but power consumption increases
Solution Approach 1:
The voltage level shifter circuit is designed to self-regulate transistor operating conditions through its inherent multi-stage architecture and voltage rail configuration. The circuit automatically keeps transistors within their safe operating area through proper voltage distribution, eliminating the need for external discrete biasing circuits that would consume additional power.
4Reliability
If design modifications are made to avoid SOA violation, then safe operating area is maintained, but area increases
Solution Approach 1:
The multi-stage voltage level shifter structure serves multiple functions simultaneously: it performs voltage level shifting, maintains safe operating area for all transistors, and does so without requiring additional discrete components. The same transistor network that performs the voltage translation also inherently protects against SOA violations, eliminating the need for separate protective circuits that would increase area.
Data Source
AI summary
Disclosed structures include a single-stage and a multi-stage voltage level shifter. Each structure includes multiple transistors, which are optionally all symmetric low-voltage transistors, and the structures are configured to avoid operation outside the safe operating area (SOA) of such transistors. The single-stage voltage level shifter and the first stage of the multi-stage voltage level shifter can be essentially identical. In operation, input voltage pulses (including an input voltage pulse transitioning between a first positive voltage (V1) equal to the voltage rating of the transistors and ground) can be received at source nodes of N-type transistors and, in response, output voltage pulses (including an intermediate output voltage pulse transitioning between V1 and a second positive voltage (V2) that is higher than (e.g., double) V1 and an output voltage pulse that transitions between ground and V2) can be output.