Current-Mirror Level Shifter for Sub-Threshold Signal Translation
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Solution Overview
Problem
Conventional level shifter circuits fail to properly convert signals between different voltage domains when the input voltage level is lower than the threshold voltage of the transistors, leading to incorrect output signals and limited applicability in power-constrained devices.
Innovation Solution
A level shifter circuit using current mirrors, specifically a cross-coupled latch circuit coupled with first and second current mirror circuits, drives output signals from transient to steady state voltage levels, ensuring correct signal conversion even when transistors operate in sub-threshold conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional level shifter circuits are used to convert signals between voltage domains, then signal conversion is achieved when voltage levels are sufficient, but the circuit fails to properly translate signals when the input voltage level is low in comparison to transistor threshold voltages
Solution Approach 1:
The patent introduces an intermediate voltage generation mechanism using current mirrors that convert the low input voltage into a higher intermediate voltage level. This intermediary voltage then drives the output stage, effectively bridging the gap between the low input voltage domain and the higher output voltage domain, enabling reliable signal translation where conventional circuits fail
Solution Approach 2:
The patent changes the voltage parameter by using current mirror circuits to generate an intermediate voltage level that is higher than the low input voltage but lower than the final output voltage. This parameter transformation allows the circuit to operate correctly even when the input voltage is below the transistor threshold voltage
2Reliability
If current mirror circuits are added to drive output signals from transient to steady state voltage levels, then signal conversion reliability is improved, but device complexity increases
Solution Approach 1:
The current mirror circuits perform multiple functions: they generate the intermediate voltage level, drive the output stage to steady state, and ensure proper signal level translation. By making these circuits multi-functional, the patent reduces the need for additional separate components, thereby limiting the increase in overall device complexity while achieving improved reliability
Data Source
AI summary
Various implementations described herein may refer to level shifter circuitry using current mirrors. For instance, in one implementation, a level shifter circuit may include a latch circuit configured to receive an input signal, where the latch circuit includes a plurality of transistors configured to generate an output signal based on the input signal. The level shifter circuit may also include a first current mirror circuit coupled to the latch circuit. The level shifter circuit may further include a second current mirror circuit coupled to the latch circuit, where the first current mirror circuit and the second current mirror circuit are configured to drive the output signal from a transient state voltage level to a steady state voltage level.