Level Shifter Feedback Resistor for Clock Duty Cycle Control
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Solution Overview
Problem
High-speed signal transmission in semiconductor chips often experiences duty cycle distortion due to manufacturing variations, voltage, and temperature changes, making it challenging to accurately control the clock duty cycle, especially for low-amplitude signals.
Innovation Solution
A duty cycle correction method using a feedback common mode resistor is implemented, where a duty cycle correction signal is applied in the feedback path of a level shifter circuit, with the injection point being programmable, allowing for correction of duty cycle distortion in both voltage and current forms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed signal transmission is implemented, then processing speed is improved, but duty cycle distortion increases due to manufacturing variations and environmental factors
Solution Approach 1:
The patent implements a feedback mechanism by applying a duty cycle correction signal in the feedback path of the level shifter circuit. The correction signal is injected through a feedback common mode resistor, creating a closed-loop system that continuously adjusts the duty cycle to compensate for distortions caused by high-speed transmission, manufacturing variations, and environmental factors.
Solution Approach 2:
The patent changes the electrical parameters within the feedback path by injecting a correction signal that modifies the common mode voltage or current. This parameter adjustment allows dynamic compensation for duty cycle distortion without altering the fundamental high-speed transmission characteristics, enabling precise duty cycle control at high speeds.
2Speed
If low-amplitude signals are transmitted for high-speed communication, then bandwidth is improved, but duty cycle control precision deteriorates
Solution Approach 1:
The patent introduces an intermediary correction signal in the feedback path that acts as a mediator between the distorted high-speed signal and the desired duty cycle. This correction signal, applied through the feedback common mode resistor, provides fine-grained control over the duty cycle without directly interfering with the low-amplitude high-speed signal transmission, thereby maintaining both speed and precision.
3Manufacturing precision
If duty cycle correction is applied in the feedback path, then duty cycle accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent achieves multi-functionality by utilizing the existing feedback path and common mode resistor for dual purposes: maintaining stable operation of the level shifter and applying duty cycle correction. This approach integrates the correction function into the existing circuit infrastructure rather than adding separate correction circuits, thereby improving duty cycle accuracy while minimizing increases in overall circuit complexity.
Data Source
AI summary
Systems, apparatuses, and methods for applying duty cycle correction to a level shifter via a feedback common mode resistor are disclosed. A circuit includes a capacitor, an inverter, and at least one feedback resistor. An input signal is received and coupled through the capacitor to the inverter. To correct for duty cycle distortion on the input signal, a duty cycle correction signal is applied to the at least one feedback resistor in the feedback path. The duty cycle correction signal can be applied as a voltage or as a current. In one implementation, the location of the injection point for applying the duty cycle correction signal within the at least one feedback resistor is programmable.