SRAM Retention Scheme with Discrete Switch Control

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Solution Overview

Problem

In System-on-a-Chip (SoC) designs, functional blocks often experience power conservation challenges due to the need to disable and re-initialize power when not in use, leading to data loss and inefficiencies in power management, especially when transitioning between operational modes requiring different voltage levels.

Innovation Solution

A power management apparatus and method that includes a reference voltage circuit and a voltage generation circuit, which enables a comparison of output signals to stored operational states, allowing for the adjustment of voltage levels and efficient power management by disabling the reference voltage circuit after comparison, using a sense amplifier to output digital signals for state retention and adjustment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If power is disabled to conserve energy when functional blocks are not in use, then power consumption is reduced, but data and operational settings are lost requiring re-initialization

Engineering Contradiction:

Improvepower consumptionVSAvoiddata loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of information

Solution Approach 1:

The patent applies preliminary action by enabling the reference voltage circuit before the voltage generation circuit, ensuring the reference voltage is ready and stable before comparisons begin. This prevents data loss by ensuring proper initialization sequence when transitioning from low-power to operational modes, eliminating the need for complete re-initialization of functional blocks.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback through the voltage generation circuit that continuously monitors and compares output voltage levels against the reference voltage. This feedback mechanism maintains data integrity during power mode transitions by detecting when voltage levels are improper and preventing operational errors, thereby reducing data loss without requiring full re-initialization.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If active power regulating circuits are used to control voltage output, then voltage control flexibility is improved, but circuit complexity increases

Engineering Contradiction:

Improvevoltage control flexibilityVSAvoidcircuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the power regulation system into distinct functional modules: a reference voltage circuit that generates stable reference levels, a voltage generation circuit that produces output voltage, and a comparison mechanism that monitors voltage levels. This modular segmentation provides flexible voltage control while keeping each module simple and manageable, reducing overall circuit complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary reference voltage circuit that mediates between the power source and the functional blocks. This reference voltage serves as a stable intermediary standard against which output voltage is compared and adjusted, enabling flexible voltage control without requiring complex direct control mechanisms, thereby simplifying the overall circuit design.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If reference voltage circuit remains enabled continuously, then voltage regulation accuracy is maintained, but power consumption increases

Engineering Contradiction:

Improvevoltage regulation accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic action by enabling the reference voltage circuit only when needed - specifically, before voltage comparisons are performed and during operational modes. The reference voltage circuit is disabled during low-power modes when functional blocks are not in use. This periodic enabling maintains voltage regulation accuracy when required while significantly reducing power consumption during idle periods.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies dynamics by making the reference voltage circuit's operational state variable rather than static. The circuit dynamically transitions between enabled and disabled states based on the operational mode of functional blocks. This dynamic behavior maintains voltage regulation accuracy during active operation while minimizing power consumption during low-power modes, resolving the contradiction between accuracy and energy usage.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9411406B2SRAM regulating retention scheme with discrete switch control and instant reference voltage generation

Publication Date: 2016.08.09 APPLE INC

AI summary

A system including control logic, a voltage reference, a sense amplifier, and a voltage supply circuit is presented. The sense amplifier may be configured to detect a current state of the voltage supply circuit output compared to the reference voltage. The voltage supply circuit may be configured to capture and preserve the current state to be used as a previous state. The voltage regulator may be configured to compare the current state to one or more previous states and adjust the voltage regulator output based on the comparison. Control logic may be configured to enable the voltage reference output in response to a signal. Control logic may be configured to enable the sense amplifier at a time after the voltage reference is stable. Control logic may be configured to disable the voltage reference output in response to the sense amplifier generating an output.