NMOS Output Driver With Ground Termination for Faster Signaling
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Solution Overview
Problem
Conventional output drivers using PMOS transistors as pull-up drivers are inefficient due to lower carrier mobility compared to NMOS transistors, requiring larger PMOS transistors and increased current flow, which complicates data signaling and power consumption.
Innovation Solution
An integrated circuit with an output driver utilizing NMOS transistors for both pull-up and pull-down operations, including a pre-driver circuit to generate complementary signals and a termination resistor connected to ground, enhancing data transmission efficiency and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If PMOS transistors are used as pull-up drivers, then the output driver can operate with conventional structure, but the carrier mobility is lower and the transistor size must be increased
Solution Approach 1:
The patent changes the transistor type parameter from PMOS to NMOS for the pull-up driver, leveraging the higher electron mobility of NMOS transistors to achieve faster operation speeds while reducing the required transistor size compared to conventional PMOS-based designs
2Ease of manufacture
If PMOS transistors are used as pull-up drivers, then the conventional structure can be maintained, but the transistor size increases and current flow increases
Solution Approach 1:
The patent changes the transistor type parameter from PMOS to NMOS for the pull-up driver, leveraging the higher electron mobility of NMOS transistors to achieve faster operation speeds while reducing the required transistor size compared to conventional PMOS-based designs
3Speed
If NMOS transistors are used for both pull-up and pull-down, then the layout area is reduced and speed is improved, but the structure deviates from conventional design
Solution Approach 1:
The patent applies universality by using NMOS transistors for both pull-up and pull-down operations, allowing the same transistor type to perform multiple functions. This simplifies the overall device structure and reduces layout area while maintaining high-speed performance
4Power
If larger PMOS transistors are used, then the pull-up capability is sufficient, but the layout area increases and input capacitance increases
Solution Approach 1:
The patent changes the transistor type parameter from PMOS to NMOS for the pull-up driver, leveraging the higher electron mobility of NMOS transistors to achieve faster operation speeds while reducing the required transistor size compared to conventional PMOS-based designs
Solution Approach 2:
The patent applies local quality by optimizing the transistor size parameters specifically for NMOS devices, allowing smaller dimensions to achieve the same pull-up capability due to the inherently higher mobility of electrons compared to holes in PMOS transistors
Data Source
AI summary
An integrated circuit comprising an output driver including an output terminal, and a receiving circuit including a termination resistor connected between the output terminal and a ground. The output driver comprising a first NMOS transistor configured to pull up a voltage of the output terminal to a pull-up voltage in response to a pull-up signal, and a second NMOS transistor configured to pull down the output terminal to a ground voltage in response to a pull-down signal.