Level Shifter Edge Detection for High Slew Rate Rail Immunity
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Solution Overview
Problem
Level shifters face issues with output signal state changes due to high slew rate signals on the power supply rail, leading to unintended logic state transitions.
Innovation Solution
An edge detector is employed to detect high slew rate signals, initiating a current pulse boost to prevent changes in the logic state of the output signals by sinking current from the level shifter when such edges are detected, using a combination of positive and negative edge detectors and logic circuits to generate a boost signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a level shifter operates without edge detection protection, then the device complexity is reduced, but the reliability deteriorates due to unintended logic state transitions caused by high slew rate signals on the power supply rail
Solution Approach 1:
The edge detector proactively detects high slew rate transitions on the power supply rail before they can cause unintended logic state changes in the level shifter output. By initiating a current pulse boost in advance, the system prevents erroneous state transitions rather than correcting them after occurrence, thereby improving reliability without requiring complex feedback correction circuits.
Solution Approach 2:
The edge detector acts as an intermediary component that monitors the power supply rail and mediates between the power supply disturbances and the level shifter. When a high slew rate edge is detected, it triggers a current pulse through the current mirror circuit that counteracts the harmful effects of the power supply transient, protecting the output signals without requiring direct modification of the level shifter structure.
2Reliability
If a current pulse boost is initiated in response to detected edges, then the immunity to state changes improves, but the use of energy increases due to frequent current pulses during high-frequency ringing conditions
Solution Approach 1:
The system dynamically adjusts its power consumption based on the electrical conditions of the power supply rail. During normal operation with stable power supply, the edge detector remains inactive and power consumption is minimal. When high slew rate edges are detected indicating ringing or transient conditions, the system activates the current pulse boost temporarily to maintain immunity to state changes, thereby optimizing the balance between reliability and energy consumption.
Solution Approach 2:
The current pulse boost operates periodically only when triggered by detected edges on the power supply rail, rather than continuously. This periodic activation based on actual need ensures that energy is consumed only when protection is required, preventing unnecessary power waste during stable operating conditions while maintaining reliability during transient events.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents unintended logic state changes in level shifter output signals during high slew rate events on the power supply rail, ensuring stable operation even under high-frequency ringing conditions.
Implementation Method 1
a capacitor coupled between the second supply voltage and the second path of the current mirror, wherein a current flowing through the capacitor when a positive going edge on the second supply voltage meets or exceeds the first predetermined slew rate causes the positive edge detector output node to be pulled to a high voltage level
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
An integrated circuit (IC) includes a level shifter coupled to receive a first supply voltage and a second supply voltage and configured to generate a first output signal and a second output signal in response to an input command signal and an edge detector configured to detect an edge on the second supply voltage and to sink a current from the level shifter in response to detection of the edge in order to prevent a change in logic state of the first output signal or the second output signal. The edge detector can include a positive edge detector configured to generate a positive edge signal in response to detection of a positive going edge of greater than a first predetermined slew rate and a negative edge detector configured to generate a negative edge signal in response to detection of a negative going edge of greater than a second predetermined slew rate.