Quadrature Duty Cycle Correction Circuit With Low-Latency 50% Output
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Solution Overview
Problem
Existing duty cycle correction circuits for high-frequency clock signals consume substantial power and semiconductor die area, and often have significant latency in achieving the desired duty cycle.
Innovation Solution
A duty cycle correction circuit using a combination of NMOS and PMOS transistors arranged in serial pairs to process quadrature clock signals, achieving a corrected 50% duty cycle with minimal power consumption and die space, by switching transistors in response to specific quadrature clock signal phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional duty cycle correction circuits are used, then duty cycle correction is achieved, but power consumption increases substantially
Solution Approach 1:
The correction circuit is segmented into four distinct transistor pairs (first through fourth pairs), each pair handling specific quadrature clock phases. This segmentation allows the circuit to process clock signals in discrete stages, reducing the simultaneous switching activity and associated power consumption compared to conventional monolithic correction circuits.
Solution Approach 2:
The circuit utilizes periodic quadrature clock signals (90-degree phased signals) to control the switching of transistor pairs in a periodic manner. Each transistor pair is activated during specific phases of the clock cycle, creating a periodic switching pattern that reduces average power consumption while maintaining continuous duty cycle correction.
2Manufacturing precision
If conventional duty cycle correction circuits are used, then duty cycle correction is achieved, but semiconductor die area increases substantially
Solution Approach 1:
By segmenting the correction function into four specialized transistor pairs, each optimized for specific clock phases, the circuit achieves efficient space utilization. Each pair can be compactly designed for its specific function, and the segmented architecture allows for optimized layout that reduces overall die area compared to conventional general-purpose correction circuits.
Solution Approach 2:
Each transistor pair is designed with local optimizations tailored to its specific function in the duty cycle correction process. The circuit employs different transistor configurations and sizing strategies in different locations (pairs 1-4) based on their specific switching requirements, achieving area efficiency through localized design optimization rather than a uniform approach.
3Manufacturing precision
If conventional duty cycle correction circuits are used, then duty cycle correction is achieved, but latency increases substantially
Solution Approach 1:
The circuit performs preliminary duty cycle correction by using the quadrature clock phases to proactively control transistor switching before the full clock cycle completes. The segmented transistor pairs begin correcting duty cycle deviations in early clock phases, reducing the time required to achieve the desired 50% duty cycle compared to conventional circuits that wait for full cycle detection.
Solution Approach 2:
The duty cycle correction operates continuously through all four quadrature clock phases with no idle periods. Each transistor pair is actively engaged during its designated phase, ensuring continuous correction action throughout the entire clock cycle. This eliminates latency associated with conventional circuits that may have discrete correction stages with transition delays between them.
Data Source
AI summary
A duty cycle correction circuit includes four pairs of serially coupled transistors. A first two of the serial pairs of transistors couple between an internal node for complement output clock signal and ground. A second two of the serial pairs of transistors couple between the internal node and a power supply node for a power supply voltage. Each serial pair is controlled by a corresponding pair of quadrature clock signals in which one of the quadrature clock signal is delayed with respect to the other quadrature clock signal be one quarter of a clock period. The first two serial pairs of transistors thus combine to discharge the internal node for one-half clock period whereas the second two serial pairs of transistors combine to charge the internal node for one-half clock period so that the complement output clock signal has a 50% duty cycle.