Freeze-Enabled Level Shifter Circuit for Thin-Oxide Power Domains

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Solution Overview

Problem

Existing freeze circuits for level shifters require thick-gate-oxide transistors to handle voltage stress, which are costly and may not be available on advanced process nodes, posing a challenge in power domain management.

Innovation Solution

A freeze circuit design using thin-gate-oxide transistors with tri-state inverters and a controller to manage power domains, allowing the level shifter to be placed in a known state during power collapse without the need for thick-gate-oxide transistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thick-gate-oxide transistors are used in freeze circuits to handle voltage stress, then reliability is improved, but manufacturing cost increases and availability decreases on advanced process nodes

Engineering Contradiction:

Improvevoltage stress handling capabilityVSAvoidmanufacturing cost and availability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the gate oxide thickness parameter from thick to thin, enabling the use of standard thin-gate-oxide transistors available on advanced process nodes while maintaining reliability through circuit-level protection mechanisms including freeze circuits and voltage stress management techniques

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If power domains are collapsed to conserve power, then energy efficiency is improved, but signal integrity maintenance becomes more difficult

Engineering Contradiction:

Improvepower consumptionVSAvoidsignal integrity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-charging hold capacitors and setting level shifter inputs to known states before power collapse occurs. The freeze circuit is activated in advance to discharge capacitors and establish deterministic initial conditions, ensuring signal integrity is maintained when power is restored

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces freeze circuits and hold capacitors as intermediary elements between the power domain and the level shifter. These intermediaries maintain signal integrity during power collapse by holding voltages at defined levels and preventing undefined states, acting as a buffer between the collapsed power domain and active circuits

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12470219B2Freeze enabled swing level shifter

Publication Date: 2025.11.11 QUALCOMM INC

AI summary

A system includes a circuit in a first power domain, a first tri-state inverter having an input coupled to the circuit, and a second tri-state inverter having an input coupled to an output of the first tri-state inverter. The system also includes a level shifter in a second power domain, wherein the level shifter has a first input coupled to the output of the first tri-state inverter and a second input coupled to an output of the second tri-state inverter. The system also includes a shunt switch, a controller, and a pass gate. The shunt switch is coupled between the first input of the level shifter and ground or coupled between the second input of the level shifter and ground. The pass gate is coupled between the controller and the second input of the level shifter or coupled between the controller and the first input of the level shifter.