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 the 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 first voltage domain, allowing the cross-latch circuit to operate in a higher voltage domain, thereby enhancing the level shifting process and increasing operational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If input signals in lower voltage domains 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 transition, allowing the cross-latch circuit to operate in a higher voltage domain while the input signals remain in the lower voltage domain. This resolves the contradiction by adding a mediating element that enables faster operation without directly complicating the core cross-latch structure.
2Device complexity
If input signals in lower voltage domains are directly applied to cross-latch circuits, then device complexity is reduced, but reliability deteriorates
Solution Approach 1:
The tracking circuit serves as a reliability-enhancing intermediary that ensures proper voltage level translation. By generating overdrive signals that explicitly control the cross-latch circuit's voltage domain transitions, the system achieves more reliable operation compared to direct signal application, which may suffer from undefined voltage levels during transitions.
Solution Approach 2:
The tracking circuit performs preliminary action by pre-generating the appropriate overdrive signals before the cross-latch circuit needs to switch states. This preliminary signal preparation ensures that the cross-latch circuit receives properly conditioned voltage levels in advance, improving reliability by preventing undefined or marginal voltage states during critical switching operations.
3Speed
If overdrive signals are provided to cross-latch circuit based on input signals, then operational speed is improved, but device complexity increases
Solution Approach 1:
The patent segments the level shifter into distinct functional modules: an input circuit for receiving signals, a tracking circuit for generating overdrive signals, and a cross-latch circuit for voltage domain conversion. This segmentation allows each module to be optimized independently for speed while maintaining overall system manageability, resolving the contradiction by organizing complexity into manageable segments rather than a monolithic structure.
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.