Single-Supply Voltage Level Shifter With Leakage-Blocking Control
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Solution Overview
Problem
Conventional single supply digital voltage level shifters experience high leakage currents and limited operating speed due to threshold voltage drops and diode-connected transistors, restricting their range of input signals and power supply, and requiring a large physical footprint.
Innovation Solution
A single supply digital voltage level shifter design incorporating a first and second inverter, a comparison stage, and a control stage with a switch that assumes a non-conducting state based on the comparison stage output, reducing leakage current and eliminating the need for a second power rail, thereby minimizing footprint and enhancing flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional single supply level shifter is used, then the footprint is reduced compared to dual supply architectures, but leakage current increases significantly
Solution Approach 1:
The level shifter is divided into two independent inverters (first inverter and second inverter) with separate threshold voltage compensation paths. The first inverter handles the input signal at VDDL while the second inverter outputs at VDDH, with each stage having its own threshold compensation mechanism that prevents leakage current propagation between voltage domains.
Solution Approach 2:
A threshold voltage compensation circuit acts as an intermediary between the first and second inverters. This compensation circuit generates control signals that adjust the switching thresholds of the inverters, preventing the diode-connected transistor from creating continuous leakage paths while maintaining proper level shifting functionality across different voltage domains.
2Device complexity
If a diode-connected transistor is used for threshold compensation, then the circuit operates with single supply, but the operating speed is limited
Solution Approach 1:
The inverter thresholds are made dynamic through feedback control rather than being fixed by diode-connected transistors. The threshold voltage compensation circuit dynamically adjusts the gate voltages of the inverter transistors based on the operating conditions, allowing the circuit to maintain simplicity while achieving higher operating speeds by optimizing thresholds in real-time.
3Adaptability or versatility
If the voltage difference between VDDH and VDDL exceeds the threshold voltage, then level shifting is achieved, but leakage current increases
Solution Approach 1:
The threshold voltage compensation circuit uses feedback from the actual voltage levels at the inverter nodes to dynamically adjust the switching thresholds. This feedback mechanism ensures that the inverters operate correctly even when the voltage difference between VDDH and VDDL varies, while the compensation prevents leakage current by ensuring proper transistor cutoff when signals are at opposite logic levels.
Data Source
AI summary
A single-supply digital voltage level shifter has a first inverter having a first input for receiving an input signal with a first voltage swing, and a first output for outputting a first output signal. A second inverter has a second input for receiving the first output signal, and a second output for outputting a second output signal with a second voltage swing, where the second output signal is a level-shifted version of the input signal. A comparison stage includes a first comparison stage input for receiving the input signal, a second comparison stage input for receiving the second output signal, and a comparison stage output for outputting a comparison stage output control signal. A control stage is connected in a circuit branch of the first inverter and has a control stage switch that assumes a non-conducting state dependent on a logical state of the comparison stage output control signal.