AC-Coupled Level Translator for Fast Logic Across Voltage Rails
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Solution Overview
Problem
There is a need for a high-speed AC coupled logic level translator to enable fast digital signal transmission across different supply voltage groups while maintaining signal transition speeds, particularly for high-speed, high-current CMOS drivers used in applications like medical ultrasound and switch mode power supplies.
Innovation Solution
A level translator circuit comprising a pair of complementary MOS transistors, capacitors, resistors, and clamping circuits, along with a voltage detection circuit and a flip-flop device, which couples input signals to the transistors' gates and limits gate voltages to ensure rapid signal differentiation and recharging, allowing for efficient logic level translation across voltage barriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a logic level translator is used to adapt between mismatched voltage levels, then voltage compatibility is improved, but signal transition speed deteriorates
Solution Approach 1:
The translator is divided into two independent AC-coupled channels, each handling one direction of level translation. This segmentation allows each channel to be optimized for fast signal transitions while maintaining voltage compatibility, resolving the contradiction between adaptability and speed.
Solution Approach 2:
AC coupling capacitors are introduced as intermediary elements between the low-voltage and high-voltage domains. These capacitors block DC voltage differences while allowing AC signal transitions to pass through quickly, enabling voltage compatibility without sacrificing signal transition speed.
2Speed
If AC coupling is used to maintain fast signal transitions across voltage barriers, then signal transition speed is preserved, but circuit complexity increases
Solution Approach 1:
The circuit merges multiple functions into unified structures: complementary MOS transistors perform both level translation and signal buffering, while shared capacitors and resistors serve multiple purposes in the AC coupling network. This merging reduces overall circuit complexity while maintaining fast signal transitions.
Solution Approach 2:
Each transistor and capacitor in the AC-coupled architecture performs multiple functions: transistors provide both level translation and signal amplification, while capacitors simultaneously block DC voltage differences and couple AC signals. This multi-functionality reduces the total component count and simplifies the circuit.
3Speed
If high current CMOS drivers are used for fast switching, then switching speed is improved, but power consumption increases
Solution Approach 1:
The AC-coupled architecture enables periodic charging and discharging of the coupling capacitors during signal transitions. This periodic action allows high current to flow only during brief transition periods rather than continuously, achieving fast switching while reducing average power consumption.
Solution Approach 2:
The circuit recovers energy during signal transitions by utilizing the complementary nature of the MOS transistor pairs. When one transistor switches on, the other switches off, allowing capacitive energy to be transferred and recovered rather than dissipated, reducing overall power consumption while maintaining fast switching speeds.
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 effectively enables fast and accurate logic level translation, ensuring that signal transitions are preserved across voltage differences, thereby supporting high-speed operations in applications with mismatched voltage rails.
Implementation Method 1
A first coupling capacitor is coupled to the gate of the first transistor. A second coupling capacitor is coupled to the gate of the second transistor.
Implementation Method 2
A complementary MOS field effect transistor amplifier for AC input signals has a voltage detection circuit. The voltage detection circuit has a first transistor having a first predetermined voltage threshold and a second transistor having a second predetermined voltage threshold.
Implementation Method 3
A first clamp circuit is coupled to the gate of the first transistor for limiting a gate voltage of the first transistor. A second clamp circuit is coupled to the gate of the second transistor for limiting a gate voltage of the second transistor.
Implementation Method 4
A first resistor is coupled to the gate of the first transistor and to a source of the first transistor. A second resistor is coupled to the gate of the second transistor and to a source of the second transistor.
Data Source
AI summary
A level translator has a pair of transistors, wherein a first transistor of the pair of transistors and a second transistor of the pair of transistors are complimentary. A pair of capacitors are provided, wherein a first capacitor of the pair of capacitors is coupled to a voltage input VIN and to a gate of a first transistor of the pair of complimentary transistors and a second capacitor of the pair of capacitors is coupled the voltage input VIN and to a gate of a second transistor of the pair of complimentary transistors. A flip flop device is provided having a first input coupled to a drain of the first transistor, and a second input coupled to a drain of the second transistor. A pair of resistors is provided, wherein a first resistor of the pair of resistors is coupled to the gate of the first transistor and to a voltage supply of VDD, and a second resistor of the pair of resistors is coupled to the gate of the second transistor and to a voltage supply VSS. A pair of clamping circuits is provided, wherein a first clamping circuit of the pair of clamping circuits is coupled to the gate of the first transistor and to a voltage supply of VDD, and a second clamping circuit of the pair of clamping circuits is coupled to the gate of the second transistor and to a voltage supply VSS.