Selectable-Inverter Delay Cell for Precise Timing Adjustment
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Solution Overview
Problem
Conventional delay cells face challenges in efficiently adjusting signal timing between devices with different operation speeds, leading to slope loss and increased Process-Voltage-Temperature (PVT) variations due to the need for additional inverters to compensate for delay value requirements.
Innovation Solution
A delay cell configuration that includes a first inverter, a second inverter coupled between the first and output terminals, and additional inverters coupled in parallel, with a delay element controlling the additional inverters' connection to the input terminal via a control signal, allowing for selective adjustment of delay values by sequential turn-on timings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional inverters are used to compensate for delay value requirements, then the delay range is extended, but slope loss and PVT variations increase
Solution Approach 1:
The patent implements dynamic control of inverter activation through a delay element that selectively couples additional inverters to the input terminal based on control signals. This allows the delay cell to adaptively activate only the necessary number of inverters for the required delay value, avoiding the static presence of multiple inverters that causes slope loss and PVT variations while still providing extended delay range capability.
Solution Approach 2:
The delay cell is segmented into a first inverter, second inverter, and additional inverters that can be selectively activated. The delay element divides the control function by selectively coupling specific additional inverters to the input terminal, allowing independent control of each inverter group. This segmentation enables precise delay adjustment without permanently connecting all inverters, thereby reducing slope loss and PVT variations.
2Adaptability or versatility
If multiple additional inverters are permanently connected, then various delay values can be supported, but device complexity increases
Solution Approach 1:
The delay element provides dynamic reconfiguration capability by selectively coupling additional inverters to the input terminal based on control signals. This dynamic approach replaces the need for multiple permanent inverter configurations, allowing the same hardware structure to support various delay values through controlled activation rather than physical reconfiguration.
Solution Approach 2:
The delay cell structure with selectively coupleable additional inverters serves multiple functions: it can support various delay values, reduce slope loss, and minimize PVT variations. The same basic configuration (first inverter, second inverter, and delay element) universally handles different delay requirements without needing separate inverter chains for each delay value.
Data Source
AI summary
A delay cell may include: a first inverter coupled to an input terminal; a second inverter coupled between the first inverter and an output terminal; an additional inverter coupled in parallel to the first inverter; and a delay element suitable for selectively coupling the additional inverter to the input terminal under control of a control signal.