4T SRAM Pixel Circuit Anti-Floating Design
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Solution Overview
Problem
Existing pixel circuits require a large number of transistors, leading to increased size and potential voltage floating issues when using reduced transistor counts, such as in 4T SRAMs, which complicates stable data storage in micro LED displays.
Innovation Solution
A pixel circuit design utilizing 4T SRAM cells with specific transistor configurations and an anti-floating transistor to manage threshold voltage differences and prevent voltage floating, along with a reduced PWM control unit transistor count, allowing for stable data storage and smaller circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If 4T SRAM is used to reduce transistor count, then pixel circuit size is reduced, but voltage floating problem occurs leading to unstable data storage
Solution Approach 1:
The patent changes the threshold voltage parameter of transistors by introducing a body bias voltage through a dedicated body contact. By applying different voltages to the body terminal of the 4T SRAM transistors, the threshold voltage is dynamically adjusted to prevent voltage floating and ensure stable data storage while maintaining the reduced transistor count
Solution Approach 2:
The patent introduces a body bias voltage as an intermediary control mechanism. This body bias voltage acts as a mediator that indirectly controls the threshold voltage of the SRAM transistors, allowing the circuit to maintain stable operation without requiring additional transistors for direct threshold voltage control
2Area of stationary object
If transistor count is reduced for micro LED displays, then pixel circuit size decreases, but voltage floating issues arise
Solution Approach 1:
The patent modifies the electrical parameters of the 4T SRAM by introducing body biasing. By changing the body voltage parameter, the threshold voltage of the transistors is adjusted to prevent voltage floating, thereby eliminating the harmful effect while maintaining the compact pixel circuit area required for micro LED displays
Data Source
AI summary
The present specification provides a pixel circuit miniaturized using a smaller number of transistors as compared with the related art. A 4T static random-access memory (SRAM) is used in an embedded pixel memory, and in order to prevent a voltage floating problem from occurring in a logic low state, a leakage current is designed to flow in one direction by adjusting a threshold voltage of a transistor. In addition, a pulse width modulation (PWM) control unit uses a smaller number of transistors as compared with the related art, and in order to prevent a voltage floating problem from occurring, a circuit capable of removing a floating voltage is provided.