Conditional Body-Biased Level Shifter for Sub-0.45 V Operation
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Solution Overview
Problem
Conventional level shifting circuits are not functional at very low supply voltage levels, specifically below 0.45 V, when voltage shifting signals between power supply domains.
Innovation Solution
A level shifting circuit that includes a first input transistor with a gate receiving an input signal and a body terminal configured to receive a bias signal, along with a bias generator that generates bias signals based on logical combinations of the input and output signals, enabling conditional body biasing of transistors to improve operation at low voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional level shifting circuits are used, then circuit simplicity is maintained, but functionality is lost at very low supply voltage levels below 0.45 V
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the body bias voltage of the transistors based on the operating conditions. The body terminal voltage is changed from a fixed reference voltage to a dynamically controlled voltage that adapts to low supply voltage conditions, enabling the circuit to function reliably below 0.45V by modifying the transistor threshold characteristics through parameter change.
Solution Approach 2:
The patent implements dynamics by transitioning from static body biasing to dynamic body biasing. The body terminal voltage is now controlled by a bias circuit that responds to input signal conditions and supply voltage levels, making the circuit adaptable and functional across varying voltage conditions rather than being fixed for a specific operating point.
2Reliability
If body biasing is added to enable low voltage operation, then functionality at low voltage is improved, but circuit complexity increases
Solution Approach 1:
The patent uses an intermediary bias circuit that generates the appropriate body terminal voltage based on control signals. This intermediary component mediates between the input signals and the transistor body terminals, providing the necessary voltage adjustment without requiring complex direct control mechanisms, thus enabling low-voltage operation with manageable complexity.
Solution Approach 2:
The body biasing circuit is designed to serve multiple functions: it enables low-voltage operation, maintains proper transistor switching characteristics, and adapts to different supply voltage conditions. This multi-functionality reduces the need for separate circuits for different operating modes, managing the overall complexity while achieving reliable low-voltage performance.
3Productivity
If standard level shifting is used, then circuit design is simple, but operating frequency is limited and leakage current is high at low voltage
Solution Approach 1:
The patent reduces leakage current and improves operating frequency by dynamically changing the body bias parameter. By adjusting the body terminal voltage, the transistor threshold voltage is modified to optimize switching speed and reduce subthreshold leakage, directly addressing both productivity and energy loss concerns at low supply voltages through parameter optimization.
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
Enables functionality at very low supply voltage levels, increases operating frequency, and reduces leakage current in the range of 0.45 V to 0.6 V, effectively addressing the limitations of existing circuits.
Implementation Method 1
the body terminal of input transistor 112 is configured to receive a bias signal
Data Source
AI summary
A level shifting circuit receives a first input signal and complement of the first input signal as inputs and generates a level shifted first output signal and complement of the first output signal as outputs. The level shifting circuit includes a number of transistors that support body biasing. One set of body bias signals applied to certain ones of those transistors is generated as a function of the logical combination of the first input signal and the first output signal. Another set of body bias signals applied to certain other ones of those transistors is generated as a function of the logical combination of the complement of the first input signal and the complement of the first output signal. The conditional body bias applied to the transistors of the level shifting circuit makes the circuit operational for level shift at very low supply voltage levels.