Output Buffer Pre-Buffer Filtering for Stable High-Speed I/O
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Solution Overview
Problem
High-frequency data input/output in electronic devices challenges the capability of output buffers to maintain signal integrity due to variations in output resistance and supply voltage, affecting the accuracy of output data.
Innovation Solution
The implementation of pre-buffer voltage supply filtering using a portion of the total capacitance for each pre-buffer driving final NMOS and PMOS transistors, in addition to the remaining capacitance between voltage supply lines, stabilizes the gate voltage of these transistors, improving output buffer capabilities without requiring additional total capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large capacitance is used to stabilize the supply voltage applied to the output buffer, then the supply voltage stability is improved, but the physical size of the device increases
Solution Approach 1:
The patent divides the single large capacitance into multiple smaller capacitances distributed across different pre-buffers. Each pre-buffer has its own capacitance connected between its supply voltage lines, achieving overall supply voltage stability through distributed smaller capacitors rather than one large capacitor, thus reducing the total area required.
Solution Approach 2:
The patent applies capacitance locally at each pre-buffer stage rather than using a single large capacitance globally. Each pre-buffer receives tailored capacitance compensation based on its specific supply voltage variations, improving the efficiency and area-utilization of the capacitance elements while maintaining overall supply stability.
2Reliability
If additional capacitance is added to stabilize supply voltage, then signal integrity is improved, but the device complexity increases
Solution Approach 1:
The patent combines the capacitance function with the existing pre-buffer circuitry by connecting capacitances directly to the supply voltage lines of each pre-buffer. This integration approach adds the necessary capacitance for signal integrity without requiring separate dedicated capacitance circuits, thereby avoiding excessive increase in device complexity.
3Measurement precision
If the output resistance of the output buffer is kept constant, then the output data accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies preliminary compensation action by connecting capacitances to the pre-buffer supply voltage lines before the signal processing occurs. This preliminary stabilization of supply voltage prevents variations in output resistance during operation, maintaining output data accuracy without requiring complex real-time adjustment circuits.
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
This approach enhances signal integrity at the output pad by reducing variance in gate voltage, allowing for better data quality and increased operational speed in electronic devices like memory devices without increasing physical size.
Implementation Method 1
using a large capacitance to stabilize the supply voltage applied to the output buffer
Implementation Method 2
The filter circuit may include a filter capacitor coupled between a filtered voltage supply line and an inverted output of the inverter
Data Source
AI summary
An electronic device may include one or more output buffers each including a pair of final p-channel metal oxide semiconductor (PMOS) and n-channel metal oxide semiconductor (NMOS) transistors, a first pre-buffer to drive the PMOS transistor, and a second pre-buffer to drive the NMOS transistor. Each output buffer receives power from a pre-buffer supply filtering circuit, which may include a supply capacitor for stabilizing supply voltage, a low-pass first pre-buffer supply filter to filter the voltage supplied to the first pre-buffer, and a low-pass second pre-buffer supply filter the voltage supplied to the second pre-buffer.