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 to minimize current flow during data transitions.
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 causing output data noise
Solution Approach 1:
The patent applies dynamics by making the slew rate of output buffers adjustable rather than fixed. The control unit dynamically adjusts the slew rate based on the number of simultaneously switching buffers, allowing the system to optimize between speed and noise. When many buffers switch simultaneously, the slew rate is reduced to minimize noise, while when fewer buffers switch, the slew rate can be increased for faster output.
Solution Approach 2:
The patent changes the electrical parameter (slew rate) of the output buffers based on operating conditions. By measuring the number of buffers that need to switch simultaneously and adjusting the slew rate accordingly, the system adapts its performance characteristics to balance speed and noise reduction requirements.
2Speed
If slew rate is increased to improve data output speed, then switching noise increases due to larger current flow through parasitic inductance
Solution Approach 1:
The patent implements feedback by measuring the actual number of output buffers that need to switch simultaneously and using this information to adjust the slew rate. The measurement unit monitors the switching activity, and the control unit uses this feedback to optimize the slew rate, creating a closed-loop system that balances speed and noise.
Solution Approach 2:
The slew rate is made dynamic and adjustable based on real-time conditions rather than being fixed. This allows the system to increase slew rate when noise is not an issue (improving speed) and decrease it when simultaneous switching noise becomes problematic.
3Object-affected harmful factors
If slew rate is decreased to reduce simultaneous switching noise, then data output speed decreases
Solution Approach 1:
Rather than using a fixed low slew rate to reduce noise, the system dynamically adjusts the slew rate based on actual switching conditions. This allows the system to maintain high speed when few buffers switch simultaneously while reducing speed only when necessary to minimize noise from simultaneous switching.
Solution Approach 2:
The slew rate parameter is changed adaptively based on the number of simultaneously switching buffers. The system changes this electrical parameter to optimize performance, increasing it when noise is not an issue and decreasing it only when simultaneous switching noise becomes problematic.
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 output data noise by controlling slew rates, thereby minimizing the impact of simultaneous switching 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 is 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.
Data Source
AI summary
Provided is a method for reducing output data noise of a semiconductor apparatus which includes a plurality of output buffers to output data. The method includes the steps of: driving low data to a specific output buffer among the plurality of output buffers, and driving data transiting from a high level to a low level to the other output buffers; and measuring the magnitude of data noise occurring in output data of the specific output buffer, and deciding slew rates of the plurality of output buffers based on the measurement result.