Differential Level Shifter Without Capacitors for Stacked Power Domains
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Solution Overview
Problem
Existing level shifting circuits are inefficient due to large capacitors, susceptibility to supply voltage ripples, and dependency on AC-path, leading to inefficiencies and issues with signal frequency and slew rate, particularly in applications involving different voltage domains.
Innovation Solution
A level shifter apparatus that uses driver circuits operating at different voltage levels to shift input signals between power domains, employing transistor-based designs without capacitors, allowing for efficient operation in both stacked and flat modes, and enabling charge recycling for power reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors are used in traditional level shifting circuits, then voltage level shifting between power domains can be achieved, but the capacitor size becomes very large (forty times the size of other devices in the circuitry)
Solution Approach 1:
The patent removes the capacitor component entirely from the level shifting circuit, replacing it with a transistor-based design that achieves the same voltage level shifting function without requiring large energy storage elements
Solution Approach 2:
The patent replaces the traditional capacitor-based electrical energy storage mechanism with a transistor-based field effect mechanism, using electric field control to achieve level shifting without physical energy storage
2Reliability
If traditional level shifters are used, then voltage level shifting can be achieved, but they become susceptible to supply voltage ripples and uneven supply voltage values
Solution Approach 1:
The transistor-based level shifter uses the supply voltage rails directly as control signals, making the circuit self-regulating and immune to ripple effects rather than requiring separate regulation mechanisms
Solution Approach 2:
The patent changes the operating parameters by using full-rail voltage transitions (from 0 to VDD) as control signals, which provides inherent noise immunity and eliminates susceptibility to smaller ripple variations
3Reliability
If AC-path dependent level shifters are used, then signal transmission between power domains can be achieved, but issues relating to signal frequency and slew rate occur
Solution Approach 1:
The patent replaces the AC-coupled signal transmission mechanism with a direct DC-level controlled switching mechanism, eliminating frequency-dependent behavior and slew rate limitations
Solution Approach 2:
The transistor-based design serves multiple functions simultaneously: it acts as a level shifter, a buffer, and a voltage-controlled switch, providing universal operation across different signal conditions without requiring AC coupling
Data Source
AI summary
Aspects of the disclosure are directed to communications between respective power domains (circuitry) that may operate in a stacked arrangement in which the each domain operates over a different voltage range. A first circuit provides differential outputs that vary between first and second voltage levels, based on transitions of an input signal received from a first one of the power domains. First and second driver circuits are respectively coupled to the first and second differential outputs. A third driver circuit operates with the first and second circuits to level-shift the input signal from the first power domain to an output signal on a second power domain by driving an output circuit at the second voltage level in response to the input signal being at the first voltage level, and driving the output circuit at a third voltage level in response to the input signal being at the second voltage level.