Diode-Connected Voltage Level Shifter for Near-Threshold Switching
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Solution Overview
Problem
Existing integrated circuit voltage level shifters face challenges in efficiently converting low supply voltage levels to high supply voltage levels with minimal power dissipation and without requiring oversized transistors, especially at sub-threshold or near-threshold voltages, due to increased switching current and power consumption.
Innovation Solution
A voltage level shifter circuit utilizing a cross-coupled latch network with diode-connected field-effect transistors that switches at low currents, mitigating current contention between pull-up and pull-down networks by using diode-connected transistors to facilitate state changes at sub-threshold or near-threshold currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pull-down transistors are oversized to overcome pull-up current and reduce switching time, then switching speed is improved, but chip area increases and power dissipation increases
Solution Approach 1:
The diode-connected transistor is configured to pre-charge or pre-discharge the latch node in anticipation of the input signal transition. When the input signal changes state, the cross-coupled latch is already primed to switch rapidly without requiring oversized pull-down transistors, thus achieving fast switching speed without increasing chip area.
Solution Approach 2:
The diode-connected transistor acts as an intermediary element between the input signal and the cross-coupled latch. It mediates the signal transition by providing a controlled charging/discharging path that accelerates the latch switching action, eliminating the need for oversized transistors while maintaining fast switching performance.
2Loss of time
If pull-down transistors are oversized to overcome pull-up current, then switching time is reduced, but power dissipation increases
Solution Approach 1:
The diode-connected transistor pre-charges or pre-discharges the latch node in anticipation of signal transitions, reducing the time required for state changes. This preliminary action occurs with minimal current draw compared to using oversized pull-down transistors, thus reducing switching time without significantly increasing power dissipation.
Solution Approach 2:
The diode-connected transistor serves as an intermediary that accelerates latch switching through controlled charge transfer. This mediation achieves fast switching times with lower current requirements than traditional oversized pull-down transistor approaches, thereby reducing power dissipation while maintaining fast switching performance.
3Adaptability or versatility
If conventional level shifter circuitry is used at very low voltages, then voltage level conversion is achieved, but current contention increases and power dissipation increases
Solution Approach 1:
The diode-connected transistor is configured to pre-charge or pre-discharge the latch node based on the input signal state. At very low voltages, this preliminary action reduces the duration of current contention between pull-up and pull-down networks, thereby enabling voltage level conversion with reduced power dissipation.
Solution Approach 2:
The diode-connected transistor acts as an intermediary element that mediates the interaction between the input signal and the cross-coupled latch. At very low voltages, this mediation minimizes current contention by providing a controlled path for charge transfer, enabling efficient voltage level conversion with reduced power dissipation.
4Productivity
If transistor size is increased to overcome pull-up current at low supply voltage, then switching performance is improved, but chip area increases
Solution Approach 1:
The diode-connected transistor pre-charges or pre-discharges the latch node in anticipation of input signal transitions. This preliminary action enables fast switching performance without requiring oversized transistors, thus improving switching performance while maintaining compact chip area.
Solution Approach 2:
The diode-connected transistor serves as an intermediary that accelerates latch switching through controlled charge transfer. This mediation achieves high switching performance without the need for oversized transistors, thereby improving productivity while minimizing chip area occupation.
Data Source
AI summary
Some embodiments provide a voltage-level shifter circuit comprising a cross-coupled transistor pull-up network that includes a plurality of diode-connected transistors configured to cause the state of the cross-coupled transistor network to switch at a low current through a pull-down network coupled thereto, such as a current corresponding to near-threshold voltage or sub-threshold voltage operation of the pull-down network.