Semiconductor Memory Output Buffer Timing Control
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Solution Overview
Problem
Current semiconductor memory devices face challenges in reducing noise generated by simultaneous switching of multiple output buffers, which can lead to erroneous operations and slow readout rates due to increased through currents and noise levels.
Innovation Solution
A semiconductor memory device with a control circuit that manages the operation timings of multiple output buffer circuits independently using distinct control signal lines, allowing at least one buffer to operate at a different timing than others, and featuring output buffers with varying transistor current drivability and channel widths to minimize simultaneous operations and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple output buffer circuits operate simultaneously to read out data, then readout speed is improved, but noise and through current increase causing erroneous operations
Solution Approach 1:
The patent divides the simultaneous operation of multiple output buffers into sequential operations. Each output buffer circuit is controlled by a separate control signal line, allowing them to operate at different timings. This segmentation in time reduces the harmful through current and noise that would occur if all buffers switched simultaneously, while still achieving fast readout through parallel data paths.
Solution Approach 2:
The patent implements periodic or sequential operation of output buffer circuits rather than simultaneous operation. By using distinct control signal lines, the system activates output buffers in a controlled sequence, which reduces peak current demand and noise interference while maintaining high readout throughput through the time-shared access to multiple data outputs.
2Speed
If output buffer circuits are designed with high current drivability for fast operation, then readout speed is improved, but noise generation increases
Solution Approach 1:
The patent segments the operation of output buffers in time, so that not all high-current-drivable buffers operate simultaneously. This allows the system to maintain fast readout capability through parallel architecture while reducing peak noise generation by distributing the current demand across different time periods rather than concentrating it at a single moment.
3Ease of manufacture
If all output buffer circuits use identical transistor sizes for uniform performance, then manufacturing is simplified, but noise from simultaneous switching cannot be minimized
Solution Approach 1:
The patent applies different transistor characteristics (current drivability and channel width) to different output buffer circuits based on their specific operational requirements and timing schedules. This local differentiation allows optimization of each buffer's performance while minimizing simultaneous switching noise, with the understanding that manufacturing complexity is offset by the performance benefits and the use of standard CMOS processes.
Data Source
AI summary
In a semiconductor memory device for reading out multilevel data in a time-shared manner at different timings, by providing plural control signal lines for controlling the operation timings of the output buffer circuits, the operation timings of output buffer circuits can be displaced, and the number of output buffer circuits operating simultaneously can be decreased, with the result that noise is reduced. Besides, by allowing the output buffer circuit, which outputs data read out early in a time-shared manner, to operate at an early timing, data output is terminated without retarding the operation timing of the output buffer circuit operating at the last timing.