Inverter-Chain Phase Splitter for PVT-Stable 180° Phase Output
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Solution Overview
Problem
Conventional phase splitters in semiconductor integrated circuits face challenges in maintaining a consistent phase difference and duty rate of output signals due to process, voltage, and temperature (PVT) variations, as they rely on RC delay circuits that alter fan-outs.
Innovation Solution
A phase splitter design with a first and second signal path, each comprising an odd number of inverters, where the phase signals are generated and mixed to achieve a predetermined phase difference of 180 degrees, with a fan-out controller ensuring both signals have the same fan-out, thus maintaining consistent driving ability and reducing duty rate variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an RC delay circuit is used to match phase difference between signals, then the phase difference can be adjusted, but the fan-out becomes unbalanced and duty rate varies with PVT variations
Solution Approach 1:
The patent removes the RC delay circuit from the signal path entirely. Instead of using an RC circuit to adjust phase difference, the invention uses a pure inverter-based delay circuit that provides both phase inversion and delay functionality, eliminating the harmful fan-out imbalance and PVT sensitivity introduced by RC circuits
Solution Approach 2:
The inverter-based delay circuit performs multiple functions simultaneously: it provides phase inversion, time delay, and maintains balanced fan-out. This multi-functional approach replaces the separate RC delay circuit that only provided phase adjustment, thereby solving multiple problems at once
2Productivity
If the inverter 14 has fan-out of (1+α) based on RC delay circuit, then the second phase signal can be generated, but the duty rate of output signals changes with PVT variations
Solution Approach 1:
The patent applies different inverter configurations to different signal paths to achieve local optimization. The first inverter chain uses N inverters while the second uses (N-1) inverters, creating localized differences that result in the desired 180-degree phase difference while maintaining uniform fan-out characteristics throughout the circuit
Solution Approach 2:
The invention changes the fan-out parameter from unbalanced (1+α) to balanced (1) by removing the RC delay circuit. This parameter change makes the duty rate stable and insensitive to PVT variations, as the fan-out is now uniformly controlled by identical inverter stages
3Measurement precision
If different numbers of inverters are used in delay circuits to generate inverted phases, then phase difference can be achieved, but fan-out imbalance occurs
Solution Approach 1:
The patent divides the signal generation into two separate inverter chains with different lengths (N and N-1 inverters). This segmentation allows independent control of each path's delay characteristics while maintaining simple, uniform fan-out control through identical inverter cells, reducing overall device complexity
Data Source
AI summary
A phase splitter includes: a first signal path; and a second signal path, wherein the phase splitter outputs an internal signal of the first signal path as a first phase signal, and mixes an output signal of the first signal path with an output signal of the second signal path, thereby outputting a second phase signal having a predetermined phase difference from the first phase signal.