Differential Clock Skew Detector Using SR Latches
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Solution Overview
Problem
Clock skew in synchronous digital circuit systems causes variations in the timing of clock signals across different components, leading to unpredictable behavior and reduced maximum system speed due to differences in physical composition, temperature, and path length.
Innovation Solution
A differential clock skew detector using set-reset (SR) latches, which input differential clock signals 180 degrees out of phase, detects skew by varying the voltage difference between output signals, and a correction module adjusts the clock phases to minimize skew, ensuring consistent timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clock signals are distributed from a single source to all memory elements, then the circuit operation is synchronized, but clock skew occurs causing timing variations across different components
Solution Approach 1:
The patent divides the clock distribution system into multiple independent clock paths, each serving specific regions or groups of memory elements. This segmentation allows each clock path to be optimized and buffered independently, reducing the impact of skew on any single component while maintaining overall synchronization.
Solution Approach 2:
The patent introduces clock buffer elements as intermediaries between the single clock source and the memory elements. These buffers act as local clock sources that receive the master clock signal and distribute it to nearby memory elements, compensating for path length variations and reducing skew effects.
2Productivity
If the maximum system speed is increased, then productivity improves, but timing variations due to clock skew become more significant
Solution Approach 1:
The patent implements preliminary buffering of clock signals at strategic points in the distribution network. By pre-positioning buffer elements along clock paths, the system proactively compensates for timing variations before they affect memory element operation, enabling higher speeds with maintained timing precision.
Solution Approach 2:
The patent employs dynamic clock tree balancing techniques where buffer insertion and clock path routing are optimized based on actual operating conditions and load characteristics. This dynamic approach allows the system to adapt clock distribution to maximize speed while maintaining timing precision under varying operational demands.
3Measurement precision
If differential clock signals are used in SR latches, then skew detection precision improves, but device complexity increases
Solution Approach 1:
The patent uses differential signaling where complementary clock signals (CLK and CLK#) are generated as copies of each other with opposite phases. These differential copies are fed to SR latches that compare timing relationships, enabling precise skew detection through simple differential logic rather than complex measurement circuits.
Solution Approach 2:
The patent employs differential voltage levels and phase transitions as indicators of clock skew. By monitoring voltage differences and phase relationships in differential signals, the system detects timing variations through electrical state changes rather than complex temporal measurements, simplifying the detection mechanism while maintaining precision.
Data Source
AI summary
An IC chip can include a buffer and correction module that receives a set of multiphase clock signals at a given frequency, the buffer and correction module can include a differential skew detector that detects a skew between signals of the set of multiphase clock signals. The skew detector can include a set of SR latches. Differential clock signals of the set of multiphase clock signals are input into each SR latch, and the differential clock signals of the set of multiphase clock signals are set to be 180 degrees out of phase. A voltage difference between a DC component of a first output signal and a DC component of a second output signal of a respective SR latch in the set of SR latches varies as a function of the skew between the differential clock signals of the set of multiphase clock signals.