PFET Transmitter Driver With Negative Gate Boost for Wide Voltage Swing
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Solution Overview
Problem
Existing transmitter drivers using both p-type and n-type field effect transistors (PFET and NFET) face limitations in achieving a wide range of output voltage swings, leading to increased capacitance and power consumption, while drivers using only PFETs struggle with low output voltage swings, and those using only NFETs struggle with high output voltage swings.
Innovation Solution
A negative boost circuit is introduced that uses a capacitor to generate a negative voltage applied to the gate of a pull-up PFET, enhancing its strength without requiring a pull-up NFET, and includes a refresh circuit to maintain the negative boosted voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both PFET and NFET are used in the driver to achieve wide output voltage swing, then the output voltage swing range is improved, but the capacitance and power consumption increase
Solution Approach 1:
The patent removes the pull-up NFET from the driver circuit, extracting only the essential PFET component. The negative boost circuit is introduced to compensate for the limited pull-up strength of PFET alone, achieving wide output voltage swing without requiring both PFET and NFET, thus reducing capacitance and power consumption.
Solution Approach 2:
The negative boost circuit acts as an intermediary mechanism that enhances the pull-up strength of the PFET. By generating a negative voltage at the gate of the PFET, this intermediary circuit enables the PFET to achieve stronger pull-up capability comparable to having both PFET and NFET, while avoiding the capacitance penalty of using both transistor types.
2Quantity of substance
If only PFET is used in the driver, then the capacitance and power consumption are reduced, but the output voltage swing is limited
Solution Approach 1:
The patent changes the voltage parameter at the gate of the PFET by introducing a negative voltage through the negative boost circuit. This parameter change transforms the limited pull-up strength of the PFET into enhanced pull-up capability, enabling wide output voltage swing while maintaining low capacitance and power consumption characteristics of PFET-only design.
3Strength
If a negative voltage is applied to the gate of the pull-up PFET to enhance its strength, then the pull-up strength is improved, but the device complexity increases
Solution Approach 1:
The patent segments the driver function into two independent parts: the main driver circuit using only PFET for low capacitance operation, and a separate negative boost circuit for enhancing pull-up strength. This segmentation allows each circuit to be optimized independently, achieving high pull-up strength without significantly increasing overall device complexity.
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 solution allows the driver to achieve a lower output voltage swing with reduced capacitance and power consumption, while maintaining high pull-up strength, thus addressing the limitations of previous driver configurations.
Implementation Method 1
A negative boost circuit is introduced that uses a capacitor to generate a negative voltage applied to the gate of a pull-up PFET
Data Source
AI summary
A system includes a driver including a pull-up p-type field effect transistor (PFET). The system also includes a negative boost circuit. The negative boost circuit includes a first drive circuit configured to receive a first supply voltage, a second drive circuit configured to receive a second supply voltage different from the first supply voltage, a switch coupled between an output of the second drive circuit and a gate of the pull-up PFET, and a capacitor having a first terminal and a second terminal, wherein the first terminal is coupled to the gate of the pull-up PFET and the second terminal is coupled to an output of the first drive circuit. The system also includes a pre-drive circuit configured to drive an input of the first drive circuit and an input of the second drive circuit based on an input signal.