CMOS Output Driver with Common Mode Feedback for Signal Adaptation
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Solution Overview
Problem
Existing integrated circuit designs face challenges in providing output buffers that can adapt to various load impedances and signal formats, leading to inefficiencies such as extra area and power consumption, additional inventory costs, and clock jitter issues, particularly in high precision applications.
Innovation Solution
A complementary metal-oxide semiconductor (CMOS) output driver that provides a differential output signal with adjustable voltage swing and common mode voltage, using a current source and common mode feedback circuit to adapt to different load impedances, allowing for reuse of current and reducing unnecessary power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple output buffers are included to support multiple signal formats, then adaptability is improved, but area and power consumption increase
Solution Approach 1:
The patent implements a single output buffer that can operate in multiple signal formats (LVDS, LVPECL, CML) by dynamically reconfiguring its operating parameters through a configuration register. This allows one buffer to perform the functions of multiple dedicated buffers, reducing power consumption while maintaining adaptability across different signal formats.
2Adaptability or versatility
If multiple output buffers are included to support multiple signal formats, then adaptability is improved, but device area increases
Solution Approach 1:
The patent implements a single output buffer that can operate in multiple signal formats (LVDS, LVPECL, CML) by dynamically reconfiguring its operating parameters through a configuration register. This allows one buffer to perform the functions of multiple dedicated buffers, reducing die area while maintaining adaptability across different signal formats.
3Adaptability or versatility
If conversion buffers are used to interface between different signal formats, then adaptability is improved, but clock jitter increases
Solution Approach 1:
The patent uses a differential pair of transistors that directly generates the differential output signal without requiring conversion buffers. The differential pair copies the input signal while maintaining its integrity, eliminating the jitter-introducing conversion stage and providing a clean differential output suitable for high-precision applications.
4Adaptability or versatility
If separate integrated circuits are designed for each output signal format, then adaptability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements a single output buffer that can operate in multiple signal formats (LVDS, LVPECL, CML) by dynamically reconfiguring its operating parameters through a configuration register. This allows one buffer to perform the functions of multiple dedicated buffers, reducing die area while maintaining adaptability across different signal formats.
Data Source
AI summary
A complementary metal-oxide semiconductor output driver provides a differential output signal having a particular differential voltage swing and a particular common mode voltage to a differential output node for various types of load circuits coupled to the differential output node. The load circuit may have any impedance within a particular impedance range. A current source provides a current with a variable current component that adjusts the differential voltage swing of the differential output signal. A common mode feedback circuit adjusts the common mode voltage of the differential output signal by sourcing current to the differential output node or sinking current from the differential output node. At least a portion of a current flowing into a load circuit coupled to the differential node is provided by the current source, thereby reusing current from the current source.