Cross-Latch Level Shifter With Tracking Overdrive Signals
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Solution Overview
Problem
Existing voltage level shifters face challenges in efficiently adapting digital signals between integrated circuits operating at different voltage domains, leading to performance and reliability issues due to direct application of input signals in lower voltage domains to cross-latch circuits, which limits their operational speed and flexibility.
Innovation Solution
The implementation of an over-drive level shifter circuit that includes a cross-latch circuit and a tracking circuit, where the tracking circuit provides overdrive signals based on input signals in the lower voltage domain, allowing the cross-latch circuit to operate in a higher voltage domain, thereby enhancing performance and reliability by ensuring efficient signal shifting between different voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If input signals in lower voltage domain are directly applied to cross-latch circuits, then device complexity is reduced, but operational speed and reliability deteriorate
Solution Approach 1:
The patent introduces a tracking circuit as an intermediary component between the input circuit and the cross-latch circuit. This tracking circuit generates overdrive signals that mediate the voltage domain transition, allowing the cross-latch circuit to operate reliably in the higher voltage domain while still receiving input signals from the lower voltage domain. The intermediary tracking circuit resolves the contradiction by enabling reliable signal shifting without requiring direct connection between voltage domains.
Solution Approach 2:
The level shifter is segmented into distinct functional blocks: an input circuit for receiving signals in the lower voltage domain, a tracking circuit for generating overdrive signals, and a cross-latch circuit for operating in the higher voltage domain. This segmentation allows each component to be optimized for its specific voltage domain while working together to achieve reliable signal shifting, resolving the contradiction between simplicity and reliability.
2Ease of manufacture
If input signals in lower voltage domain are directly applied to cross-latch circuits, then manufacturing simplicity is improved, but operational speed deteriorates
Solution Approach 1:
The tracking circuit changes the voltage parameter of the control signals by generating overdrive signals at a higher voltage level than the input signals. This parameter change enables the cross-latch circuit to operate at higher speeds in the higher voltage domain, as the increased voltage swing allows for faster transistor switching, thereby resolving the contradiction between manufacturing simplicity and operational speed.
3Device complexity
If conventional level shifter architecture is used, then device simplicity is maintained, but adaptability to different voltage domains deteriorates
Solution Approach 1:
The tracking circuit serves multiple functions: it tracks the input signal transitions, generates appropriate overdrive signals for the cross-latch circuit, and adapts the signal levels between different voltage domains. This multi-functionality enables the level shifter to work across different voltage domain configurations (e.g., 1.8V to 3.3V, or other combinations) without requiring fundamental architectural changes, thereby resolving the contradiction between simplicity and adaptability.
Data Source
AI summary
A level shifter includes an input circuit having first and second input terminals configured to receive complementary input signals at a first voltage level and a second voltage level. A cross-latch circuit is coupled to the input circuit, and has first and second output terminals configured to provide complementary output signals at a third voltage level and a fourth voltage level. The input circuit includes first and second control nodes configured to output first and second control signals at the first voltage level and the fourth voltage level based on the input signals. A tracking circuit is coupled to the input circuit and the cross-latch circuit, and is configured to input first and second tracking signals to the cross-latch circuit based on the first and second control signals, wherein the first tracking signal is the greater of the first control signal and the third voltage level, and the second tracking signal is the greater of the second control signal and the third voltage level.