Conditional Body-Biased Level Shifting at Very Low Supply Voltage
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Solution Overview
Problem
Conventional level shifting circuits fail to function effectively at very low supply voltage levels, particularly below 0.45 V, when 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, utilizing a cascode transistor and a current mirror circuit to conditionally bias transistors and improve voltage shifting capabilities.
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 implements dynamic body biasing where the body terminals of transistors are connected to bias voltage nodes that adjust their potential based on the operating state. This dynamic adjustment allows the circuit to maintain proper transistor operation across a wide range of supply voltages, particularly enabling functionality at very low voltages below 0.45V where conventional fixed-bias circuits fail.
Solution Approach 2:
The patent changes the operating parameters of transistors by applying variable body bias voltages to adjust the threshold voltages. This parameter modification enables the transistors to operate correctly in different voltage regimes, allowing the level shifter to function reliably from very low supply voltages (below 0.45V) up to higher voltage levels.
2Use of energy by moving object
If supply voltage is reduced to very low levels, then power consumption is reduced, but level shifting functionality is lost
Solution Approach 1:
The circuit employs dynamic body biasing that adapts to different supply voltage conditions. At very low supply voltages, the biasing circuitry adjusts the body terminal voltages to maintain proper transistor operation, enabling the level shifter to function at minimal power consumption levels while preserving functionality that would otherwise be lost.
Solution Approach 2:
By dynamically adjusting the body bias parameters based on the supply voltage level, the circuit maintains optimal transistor operation across the entire voltage range. This parameter adaptation allows the level shifter to achieve ultra-low power operation at very low voltages without sacrificing the reliability of the level shifting function.
3Reliability
If body biasing is added to transistors, then level shifting functionality at low voltages is enabled, but device complexity increases
Solution Approach 1:
The patent segments the biasing control by providing separate bias voltage nodes for different transistor groups. The first group of transistors receives bias from a first bias voltage node, while the second group receives bias from a second bias voltage node. This segmented approach allows independent optimization of biasing for different circuit sections, enabling low-voltage functionality while managing complexity through modular bias control.
Solution Approach 2:
The body biasing circuitry serves multiple functions: it enables low-voltage operation, maintains transistor performance across voltage ranges, and provides adaptive control for different operating conditions. This multi-functionality justifies the added complexity by delivering comprehensive performance benefits across the entire operating voltage range.
4Productivity
If conventional level shifting is used, then circuit operation is simple, but operating frequency is limited at low supply voltages
Solution Approach 1:
The dynamic body biasing circuitry actively adjusts transistor threshold voltages based on operating conditions, enabling faster transistor switching at low supply voltages. This dynamic control overcomes the frequency limitations of conventional static-bias circuits, allowing the level shifter to achieve higher operating frequencies even at very low supply voltage levels.
Solution Approach 2:
By changing the body bias parameters to optimize transistor switching characteristics, the circuit achieves faster operation at low voltages. The adjustable threshold voltages enable the transistors to switch more rapidly, directly increasing the operating frequency capability of the level shifter at low supply voltage conditions.
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.