Adaptive Feedback Level Shifting Circuit Across PVT Corners

Solution Overview

Problem

Conventional low-to-high level shifting circuits face challenges in ensuring the strength relationship between pull-up and pull-down paths across all process, voltage, and temperature corners, leading to issues like increased current consumption, delay, and operational failures due to the difficulty in designing a weak pull-up path that is consistently weaker than the pull-down path.

Innovation Solution

The circuit employs an adaptive feedback path with a biasing circuit that generates a bias signal to control the pull-up path, ensuring it is weaker than the pull-down path by replicating the current in the pull-down path and scaling it down for the pull-up path, using a series of transistors to maintain this strength relationship across all corners.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the pull-up path is made weaker to ensure proper level shifting operation, then the circuit functionality is improved, but the current consumption increases and delay increases

Engineering Contradiction:

Improvecircuit functionalityVSAvoidcurrent consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies dynamics by making the pull-up path strength adjustable through a control signal. The pull-up transistor's effective strength is dynamically modified by adding a second pull-up transistor that can be selectively enabled or disabled, allowing the circuit to adapt its pull-up strength based on operational requirements rather than being fixed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of pull-up path strength by introducing a control signal that modifies the effective resistance or conductivity of the pull-up path. This is achieved through the second pull-up transistor whose gate is controlled by a signal that adjusts the overall pull-up capability, thereby changing the electrical parameter of the path strength.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the pull-up path is made weaker to ensure proper level shifting operation, then the circuit functionality is improved, but the delay increases

Engineering Contradiction:

Improvecircuit functionalityVSAvoiddelay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies dynamics by making the pull-up path strength adjustable through a control signal. The pull-up transistor's effective strength is dynamically modified by adding a second pull-up transistor that can be selectively enabled or disabled, allowing the circuit to adapt its pull-up strength based on operational requirements rather than being fixed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of pull-up path strength by introducing a control signal that modifies the effective resistance or conductivity of the pull-up path. This is achieved through the second pull-up transistor whose gate is controlled by a signal that adjusts the overall pull-up capability, thereby changing the electrical parameter of the path strength.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the pull-up path strength is fixed to be weaker than pull-down path, then level shifting operation is ensured, but the design is difficult to maintain across all PVT corners

Engineering Contradiction:

Improvelevel shifting operationVSAvoiddesign complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies feedback by using a control signal that is derived from the circuit's operation to adjust the pull-up path strength. The second pull-up transistor is controlled by a signal that responds to the operational state, creating a feedback mechanism that automatically adjusts the pull-up strength to maintain proper functionality across varying conditions without requiring manual redesign.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies dynamics by making the pull-up path strength adjustable through a control signal. The pull-up transistor's effective strength is dynamically modified by adding a second pull-up transistor that can be selectively enabled or disabled, allowing the circuit to adapt its pull-up strength based on operational requirements rather than being fixed.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9000826B2Level shifting circuit with adaptive feedback

Publication Date: 2015.04.07 STMICROELECTRONICS INT NV

AI summary

An amplifier has a first pull-up path coupled between a voltage supply node and an output node, and a pull-down path coupled between the output node and a ground supply node. A second pull-up path is coupled between the voltage supply node and the output node. The second pull-up path is actuated by a feedback signal and biased by a biasing signal. An inverter circuit is operable to invert the signal at the amplifier output node to generate the feedback signal. A biasing circuit is configured to generate the biasing signal. The biasing circuit is configured to control a relative strength of the pull-down path to the second pull-up path, wherein the pull-down path is stronger than the second pull-up path in a manner that is consistently present over all PVT corners.