Adjustable Level Shifter With PVT-Independent Voltage Offset
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Solution Overview
Problem
Existing level shifters in integrated circuits face challenges in providing a controllable voltage drop, as the voltage reduction is dependent on transistor characteristics and varies with process, temperature, and operating voltage, making them incompatible across different power supply domains.
Innovation Solution
A level shifting circuit comprising first and second transistors with controlled current sources, where the currents from these sources are independent of input signals, allowing for a controllable voltage shift through a common control signal, enabling precise voltage offset between different power supply domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If source or emitter followers are used for level shifting, then voltage levels are reduced, but the voltage reduction is not controllable and varies with transistor characteristics, process, temperature, and operating voltage
Solution Approach 1:
The patent applies the dynamics principle by making the voltage shift controllable through a control voltage signal applied to the gate of the second transistor. The voltage shift amount can be dynamically adjusted by changing the control voltage, transforming the static voltage reduction of traditional followers into a dynamically controllable level shifter. This resolves the contradiction by enabling precise control over the voltage shift while maintaining the voltage level translation function.
Solution Approach 2:
The patent changes the key parameter of voltage shift from being fixed by transistor characteristics to being controllable by an external voltage signal. By using the control voltage to modulate the gate-source voltage of the second transistor, the output voltage level can be precisely adjusted. This parameter change approach allows the voltage shift to be independently controlled without being constrained by process variations, temperature, or operating voltage changes.
2Reliability
If traditional level shifters are used, then voltage translation between power supply domains is achieved, but compatibility across different power supply domains is compromised due to uncontrolled voltage drop
Solution Approach 1:
The patent implements feedback by using the output voltage of the first transistor as the control voltage for the second transistor. This creates a feedback loop where the actual output voltage level is fed back to control the level shifting amount, ensuring that the final output voltage is precisely controlled and compatible with the target power supply domain. This feedback mechanism compensates for variations in transistor characteristics and ensures accurate voltage translation.
Solution Approach 2:
The patent replaces the passive voltage reduction mechanism of traditional followers with an active control mechanism using voltage-controlled transistors. Instead of relying on fixed transistor voltage drops, the system uses controlled current sources and voltage feedback to actively regulate the output voltage level, achieving both compatibility and precision across different power supply domains.
3Device complexity
If voltage reduction depends on transistor characteristics, then simple circuit structure is maintained, but voltage shift varies with process, temperature, and operating voltage
Solution Approach 1:
The patent introduces a control voltage signal as an intermediary between the input and output, mediating the voltage shift process. This control voltage acts as a mediator that decouples the voltage shift amount from transistor characteristics, allowing stable and predictable voltage translation. The intermediary control signal enables the circuit to achieve stability across process, temperature, and voltage variations while maintaining a relatively simple transistor-based structure.
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 provides a precise and controllable voltage shift, ensuring compatibility across different power supply domains, reducing stress on transistors and improving the accuracy of voltage translation in integrated circuits.
Implementation Method 1
first and second transistors. The first transistor has a control terminal coupled to an input terminal of the level shifting circuit
Implementation Method 2
first and second controlled current sources. The current from the first controlled current source and current from the second current source are substantially independent of signals applied to the input terminal
Data Source
AI summary
Described embodiments include a level shifter that provides a voltage level shift to applied signals, the amount of voltage shift being accurately controlled and independent of PVT. The level shifter has first transistor configured as a voltage follower with the gate coupled to an input terminal of the shifter and the source coupled to a node, a diode-connected transistor coupled between the node and an output terminal of the circuit, a first controlled current source coupled to the node, and a second controlled current source coupled to the output terminal. A controller receives a bandgap-stabilized voltage, squares the stabilized voltage to produce a control signal that controls the first and second controlled current sources. The voltage shift is proportional to a digitally-controlled scale factor (K) times the stabilized voltage. The ratio of the current from the first current source to the second current source is (K+1)/K.