Multi-Stage Voltage Level Shifter for Near-Threshold Activation

Solution Overview

Problem

Voltage level shifting in modern circuitry is challenging, especially when input voltage levels are near threshold levels, as devices may not turn on even with increased device size, leading to performance issues at ultra-low core voltages and high frequencies.

Innovation Solution

A multi-stage voltage level shifting circuit with a diode-drop latch and feedback assist, utilizing thick-oxide devices and multiple transistors to facilitate voltage shifting from ultra-low core voltage to higher output voltage, enabling operation up to 300 MHz with reduced area and improved performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If device size is increased to enable turning on near threshold voltage levels, then device activation reliability improves, but circuit area increases

Engineering Contradiction:

Improvedevice activation reliabilityVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

The voltage level shifter is divided into multiple stages, with each stage containing specific transistors (first through fourth transistors in the first stage, fifth through eighth transistors in the second stage) that perform incremental voltage shifting. This segmentation allows the circuit to achieve reliable near-threshold activation without requiring a single oversized device, as each transistor operates within its optimal voltage range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces intermediate voltage nodes (first intermediate voltage node and second intermediate voltage node) that serve as stepping stones between the input voltage and output voltage. These intermediate nodes allow gradual voltage transition through multiple smaller voltage steps rather than a single large step, enabling reliable device activation at near-threshold voltages without proportionally increasing device area.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multi-stage voltage level shifting circuit is implemented, then voltage shifting capability across wide range improves, but device complexity increases

Engineering Contradiction:

Improvevoltage shifting capabilityVSAvoidcircuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The voltage level shifter is divided into multiple stages, with each stage containing specific transistors (first through fourth transistors in the first stage, fifth through eighth transistors in the second stage) that perform incremental voltage shifting. This segmentation allows the circuit to achieve reliable near-threshold activation without requiring a single oversized device, as each transistor operates within its optimal voltage range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The circuit uses thick-oxide devices that can operate across a wide voltage range, making them universally applicable for both near-threshold and higher voltage operations. The same transistor structure serves multiple voltage domains, reducing the need for separate specialized devices for different voltage ranges and thereby managing complexity while maintaining versatility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If thick-oxide devices are used for ultra-low voltage operation, then device activation at near threshold voltages improves, but switching speed may be limited

Engineering Contradiction:

Improvedevice activation at near thresholdVSAvoidswitching speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The voltage level shifter is divided into multiple stages, with each stage containing specific transistors (first through fourth transistors in the first stage, fifth through eighth transistors in the second stage) that perform incremental voltage shifting. This segmentation allows the circuit to achieve reliable near-threshold activation without requiring a single oversized device, as each transistor operates within its optimal voltage range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs feedback mechanisms where output signals are fed back to control intermediate stages, ensuring continuous and smooth voltage transition. This continuous action prevents interruptions in the voltage shifting process, maintaining high-speed operation even when using thick-oxide devices designed for ultra-low voltage operation, as the feedback ensures optimal operating conditions are maintained throughout the transition.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS10784842B2Voltage level shifting circuitry

Publication Date: 2020.09.22 ARM LTD

AI summary

Various implementations described herein refer to an integrated circuit having a first stage and a second stage. The first stage has first transistors arranged as a diode, a first latch and feedback assist to facilitate shifting an input voltage in a first voltage domain to an output voltage in a second voltage domain. The first stage uses the diode and the first latch to reduce contention between the first latch and input transistors. The diode, the first latch and the feedback assist enable activation of the input transistors with the input voltage. The second stage has second transistors arranged as a second latch followed by output buffers that provide a buffered output voltage as feedback to the feedback assist of the first stage.