Output Buffer Slew Rate Control for Simultaneous Switching Noise
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Solution Overview
Problem
Semiconductor apparatuses experience output data noise due to simultaneous switching noise caused by parasitic inductance, which affects the reliability of the apparatus.
Innovation Solution
A method that measures the magnitude of data noise in specific output buffers and adjusts the slew rates of the output buffers based on the measurement, reducing the influence of simultaneous switching noise by controlling the slew rates in response to digital code values generated from the noise magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple output buffers simultaneously switch data from high level to low level, then data output speed is improved, but simultaneous switching noise increases due to parasitic inductance
Solution Approach 1:
The patent dynamically adjusts the slew rate of output buffers based on real-time noise measurements. The system includes a noise measurement unit that monitors output data noise and a control unit that modifies slew rates accordingly, transforming static buffer operation into dynamic adaptation to resolve the contradiction between speed and noise
Solution Approach 2:
The patent implements a feedback mechanism where output data noise is measured and used to control slew rates of output buffers. The noise measurement unit continuously monitors noise levels, and this information feeds back to the control unit which adjusts the slew rates, creating a closed-loop system that resolves the speed-noise tradeoff
2Loss of time
If slew rate of output buffers is increased to improve data output speed, then switching time is reduced, but simultaneous switching noise increases due to higher current flow
Solution Approach 1:
The system dynamically adjusts slew rates based on measured noise levels rather than using fixed high slew rates. The control unit modifies slew rate parameters in real-time, allowing fast switching when noise is low and reduced slew rates when noise becomes problematic, resolving the contradiction between switching speed and noise generation
Solution Approach 2:
The patent changes the slew rate parameter of output buffers based on noise measurement results. By adjusting this critical parameter dynamically, the system optimizes the balance between switching speed and noise generation, preventing excessive current flow that causes simultaneous switching noise
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively reduces data noise by minimizing the current flow during switching, thereby mitigating the impact of parasitic inductance-induced noise and ensuring reliable operation of the semiconductor apparatus.
Implementation Method 1
simultaneous switching noise may occur in a power supply voltage VDDQ or ground voltage VSSQ supplied to the output buffers BUF0 to BUFn when a plurality of data transit at the same time. For example, when a plurality of data transit to a high level to a low level, a large current IL1 may be passed to the ground voltage source VSSQ, and simultaneous switching noise VL1 may occur in the supplied ground voltage VSSQ due to parasitic inductance L1 of the ground voltage terminal.
Implementation Method 2
The respective output buffers BUF0 to BUFn of the output buffer section 10 drive high data from a power supply voltage VDDQ, and drive low data from a ground voltage VSSQ.
Data Source
AI summary
Provided is a semiconductor apparatus which includes a plurality of output buffers configured to connect a plurality of power sources, and a data noise measuring unit configured to fix an output data of a selected output buffer among the plurality of output buffers to have a specific level, measure a noise of the output data using a capacitance and control a slew rate of the plurality of output buffers based on the noise.