Differential Level Shifter for Cross-Domain Sense Amplifier Outputs
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Solution Overview
Problem
In computing devices, voltage level differences between power domains can cause short-circuit currents, leading to increased power consumption and potential circuit malfunctions when signals are transmitted without proper level shifting.
Innovation Solution
A level shifter is used to shift the voltage level of signals from a first power domain to a second power domain, utilizing a pair of transistors to generate a level shifted differential output signal, which is then stored and processed by a latch in the second power domain, thereby eliminating short-circuit currents and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a signal generated in a first power domain with a lower supply voltage level is provided to circuitry in a second power domain with a higher supply voltage level without level shifting, then the circuit structure remains simple, but short circuit current occurs leading to increased power consumption and potential circuit malfunctions
Solution Approach 1:
A level shifter circuit is introduced as an intermediary component between the first power domain (lower voltage) and the second power domain (higher voltage). The level shifter includes transistors configured to receive the differential output signal from the sense amplifier in the first power domain and generate a level-shifted differential output signal at the higher voltage level for the second power domain. This intermediary structure prevents direct voltage level conflicts that would cause short circuit current, thereby reducing power consumption while maintaining circuit functionality.
2Reliability
If transistors in the second power domain are operated without complete turn-off capability due to voltage level mismatch, then the circuit operation remains continuous, but power consumption increases and circuit malfunctions may occur
Solution Approach 1:
The level shifter circuit changes the voltage level parameter of the signal from the first power domain to match the second power domain. By transforming the voltage levels through the level shifter's transistor network, the signal parameters are adjusted so that transistors in the second power domain can operate reliably with proper voltage margins, enabling complete turn-off capability when required. This parameter transformation ensures both reliable circuit operation and reduced power consumption by preventing leakage currents from incomplete transistor turn-off.
3Reliability
If the level shifter uses a differential output signal from the sense amplifier, then the signal integrity is maintained, but timing delays in the signal path may increase
Solution Approach 1:
The level shifter circuit is segmented into multiple transistor stages that process the differential signal in parallel paths. The differential output signal from the sense amplifier is split across symmetric transistor networks, allowing the signal to be level-shifted through multiple smaller steps rather than a single large transformation. This segmentation maintains signal integrity by preserving the differential nature of the signal while reducing the timing delay associated with each individual transistor stage, as the signal propagation time is distributed across parallel paths.
Data Source
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AI summary
An apparatus includes a sense amplifier that has a sense amplifier differential output. The sense amplifier is in a first power domain. The apparatus includes level shifting circuitry that has a level shifter differential output. The level shifting circuitry is coupled to the sense amplifier differential output. The level shifting circuitry includes a first transistor and a second transistor. A first sense amplifier output of the sense amplifier differential output is coupled to the first transistor, and a second sense amplifier output of the sense amplifier differential output is coupled to the second transistor. The apparatus further includes a latch to store data. The latch is coupled to the level shifter differential output. The latch is in a second power domain that is different from the first power domain.