Adaptive Feedback Level Shifting Circuit Across PVT Corners
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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 a biasing circuit to generate a bias signal that replicates the current in the pull-down path, ensuring the pull-up path is weaker by scaling the replica current, and using adaptive feedback paths with p-channel MOSFETs to maintain the required strength relationship across all corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pull-up path is made weak to ensure proper strength relationship with pull-down path, then the circuit reliability is improved, but the delay increases
Solution Approach 1:
The patent applies dynamics by making the pull-up path strength adjustable through a control signal. The pull-up transistor's conductivity is dynamically modulated based on the state of the pull-down path, allowing the circuit to adapt its characteristics in real-time rather than being fixed. This enables the pull-up path to be weak when needed for reliability but can be strengthened when speed is critical.
Solution Approach 2:
The patent changes the electrical parameters of the pull-up path by introducing a control signal that adjusts the conductivity of the pull-up transistor. By varying the control signal level, the effective resistance and current-driving capability of the pull-up path are modified, allowing optimization of both strength and speed characteristics under different operating conditions.
2Reliability
If the pull-up path is made weak to ensure proper strength relationship with pull-down path, then the circuit reliability is improved, but the current consumption increases
Solution Approach 1:
The patent uses dynamic control to adjust the pull-up path strength based on actual circuit needs. The control signal dynamically enables or disables the pull-up transistor, allowing the circuit to consume minimal current when the pull-up function is not needed while providing full drive capability when required. This eliminates the need for a permanently weak pull-up path that would continuously consume excess current.
Solution Approach 2:
The patent modifies the electrical parameters of the pull-up path by introducing a control signal that adjusts the transistor's on-resistance and current capability. When the control signal indicates the pull-down path is active, the pull-up path parameters are changed to be weaker, reducing current consumption. When the pull-down path is inactive, the pull-up path can be strengthened, optimizing current efficiency.
3Reliability
If the pull-up path is made excessively weak to account for all PVT corners, then the circuit reliability is improved, but the delay increases significantly
Solution Approach 1:
The patent implements feedback by monitoring the state of the pull-down path and using this information to adjust the pull-up path strength. The control signal is generated based on the pull-down path activity, creating a closed-loop system that automatically adapts the pull-up transistor's conductivity. This feedback mechanism allows the circuit to maintain optimal performance across PVT corners without requiring an excessively weak fixed pull-up path.
Solution Approach 2:
The patent applies dynamics by making the pull-up path strength adjustable through a control signal. The pull-up transistor's conductivity is dynamically modulated based on the state of the pull-down path, allowing the circuit to adapt its characteristics in real-time rather than being fixed. This enables the pull-up path to be weak when needed for reliability but can be strengthened when speed is critical.
4Reliability
If a fixed weak pull-up path is used to ensure proper strength relationship, then the circuit reliability is improved, but the device complexity increases
Solution Approach 1:
The patent implements feedback by monitoring the state of the pull-down path and using this information to adjust the pull-up path strength. The control signal is generated based on the pull-down path activity, creating a closed-loop system that automatically adapts the pull-up transistor's conductivity. This feedback mechanism allows the circuit to maintain optimal performance across PVT corners without requiring an excessively weak fixed pull-up path.
Solution Approach 2:
The patent applies universality by using a single control signal to simultaneously achieve multiple objectives: maintaining proper strength relationship across PVT corners, optimizing current consumption, and minimizing delay. The control signal serves multiple functions by dynamically adjusting the pull-up path characteristics based on the operational state, eliminating the need for separate design mechanisms for each objective.
Data Source
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.