Flying Capacitor Memory Driver for Voltage Stress Tolerance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional memory driver circuits based on cross-coupled level shifter circuits face performance issues due to high threshold voltage of thick-oxide semiconductor devices, leading to increased power consumption and noise, which limits their ability to achieve competitive power, performance, and area (PPA) specifications.
Innovation Solution
The implementation of a memory driver circuit using a flying capacitor circuit, which includes a pair of thick-oxide and thin-oxide PMOS and NMOS transistors cross-coupled to protect thin-oxide transistors from voltage stress, allowing for level-shifting of input signals and reducing voltage across thin-oxide devices within their tolerance limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cross-coupled level shifter circuits are used in memory driver circuits, then level shifting function is achieved, but power consumption increases and noise increases
Solution Approach 1:
The circuit is divided into two distinct paths: a thick-oxide transistor path for voltage stress tolerance and a thin-oxide transistor path for low-power operation. This segmentation allows each path to be optimized for its specific function, resolving the contradiction between reliability and power consumption.
Solution Approach 2:
A flying capacitor is introduced as an intermediary element to transfer signals between the thick-oxide and thin-oxide transistor paths. This mediator enables the thick-oxide path to provide voltage stress tolerance while the thin-oxide path maintains low power consumption, as the capacitor isolates the two paths during signal transfer.
2Reliability
If thick-oxide semiconductor devices are used for voltage stress tolerance, then reliability improves, but threshold voltage increases leading to higher power consumption
Solution Approach 1:
The circuit segments transistor functions by oxide thickness, dedicating thick-oxide transistors to voltage stress tolerance in the level shifting path while using thin-oxide transistors for the output path where low power consumption is critical. This segmentation resolves the contradiction by assigning each transistor type to its optimal operational role.
Solution Approach 2:
Different regions of the circuit use different oxide thicknesses based on local requirements: thick-oxide transistors are placed where voltage stress tolerance is needed (level shifting path), while thin-oxide transistors are placed where low power consumption is needed (output path). This local quality differentiation resolves the contradiction between voltage stress tolerance and power consumption.
3Use of energy by moving object
If thin-oxide transistors are used to reduce power consumption, then power efficiency improves, but voltage stress tolerance decreases
Solution Approach 1:
The circuit segments the transistor paths by oxide thickness, placing thin-oxide transistors in the output path for low power consumption while protecting them from voltage stress through the thick-oxide transistor path and flying capacitor isolation. This segmentation allows thin-oxide transistors to operate efficiently without suffering from voltage stress.
Solution Approach 2:
The circuit provides beforehand protection to thin-oxide transistors by using thick-oxide transistors and a flying capacitor to isolate and protect the thin-oxide path from voltage stress before the stress can affect the thin-oxide devices. This prior cushioning enables thin-oxide transistors to operate at low power without suffering from voltage stress damage.
4Reliability
If conventional level shifter circuits are used, then level shifting is achieved, but switching noise increases
Solution Approach 1:
The circuit segments the switching operations between thick-oxide and thin-oxide transistor paths, with the flying capacitor isolating the noisy thick-oxide switching from the sensitive output path. This segmentation reduces switching noise by preventing noise propagation from the voltage stress tolerance path to the output path.
Data Source
AI summary
Embodiments relate to circuits, electronic design automation (EDA) circuit layouts, systems, methods, and computer readable media to enable logic devices operating on a core supply voltage to drive memory devices operating on a different supply voltage using low power and high data rates while avoiding voltage over-stress of thin-oxide transistors. In an embodiment, channels of a thin-oxide PMOS transistor, a thick-oxide PMOS transistor, a thick-oxide NMOS transistor, and a thin-oxide NMOS transistor are coupled in order from a memory device voltage supply rail to a low voltage supply rail. Gates of the thin-oxide PMOS transistor and the thick-oxide NMOS transistor are coupled with an output of a flying capacitor circuit that level-shifts an input signal by a difference between the memory device supply and core supply voltages, while gates of the thick-oxide PMOS transistor and the thin-oxide NMOS transistor receive the input signal via a buffer.