Level Shifter Input Latching for Noise and Leakage Suppression
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Solution Overview
Problem
Conventional level shifter circuits are susceptible to noise and leakage currents when the input power supply is powered down, leading to unreliable operation and power dissipation due to crowbar currents and erroneous outputs.
Innovation Solution
A level shifter circuit that latches input terminals to a stable supply voltage when powered down, using a keeper circuit and noise suppression components to prevent unwanted current flow and maintain logic states, thereby blocking noise-induced leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional level shifter circuit is used with powered down input supply, then power consumption is reduced, but noise susceptibility and leakage currents increase
Solution Approach 1:
The keeper circuit is activated in advance when the input power supply is powered down to preemptively latch the input terminals to a stable voltage level. This preliminary action prevents noise from affecting the inputs before any harmful effects can occur, resolving the contradiction by maintaining reliability during power-down states while preserving power savings.
Solution Approach 2:
The keeper circuit acts as an intermediary between the powered-down input supply and the rest of the level shifter circuit. It provides a stable reference voltage to the input terminals, mediating the connection and blocking noise and leakage currents from propagating through the circuit, thus maintaining reliability without compromising power efficiency.
2Loss of energy
If conventional level shifter circuit is used with powered down input supply, then power consumption is reduced, but leakage currents due to crowbar currents increase
Solution Approach 1:
The keeper circuit converts the potentially harmful situation of powered-down inputs into a beneficial state by actively latching the inputs to a stable voltage. This transforms the vulnerability of powered-down inputs into an opportunity for noise immunity and leakage current suppression, resolving the contradiction by eliminating harmful leakage currents while maintaining power savings.
Solution Approach 2:
The keeper circuit applies preliminary anti-action by preemptively preventing crowbar currents from flowing when the input supply is powered down. By latching the inputs to a stable voltage before any leakage currents can develop, the circuit blocks the harmful effect in advance, resolving the contradiction between power savings and leakage current elimination.
3Device complexity
If input terminals are left floating when powered down, then circuit simplicity is maintained, but noise-induced erroneous outputs occur
Solution Approach 1:
The keeper circuit provides self-service by automatically latching the input terminals to a stable voltage when the input power supply is powered down. This self-activating mechanism maintains output accuracy without requiring external control signals or complex additional circuitry, resolving the contradiction by ensuring reliable outputs while minimizing circuit complexity.
Data Source
AI summary
A level shifter circuit is disclosed that gates at least one of a plurality of input terminals of a level shifter to at least one of a plurality of supply voltages that are associated with respective supply voltage domains when the at least one of the plurality of supply voltages is powered down. The level shifter is therefore insensitive to noise on the input terminals and also reduces leakage current associated with noise induced crowbar currents.