Enable Circuit for SRAM Power Switch Leakage Control

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Solution Overview

Problem

In SRAM memory devices, switching procedures during shutdown modes can lead to Gate-Induced-Drain-Leakage (GIDL) issues due to uncontrolled voltage collapses, resulting in increased leakage paths and reduced energy savings.

Innovation Solution

A power switch control circuit is implemented with an additional enable pin to control PMOS transistors, turning them on when the VDD or VDDM voltage collapses, thereby reducing bulk to source leakage by selectively managing the gate control signals GMB and GDB, and employing a dual power scheme to manage power domains.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If power switches are turned off during shutdown mode to reduce power consumption, then energy savings are improved, but Gate-Induced-Drain-Leakage (GIDL) increases due to uncontrolled voltage collapses

Engineering Contradiction:

Improvepower consumptionVSAvoidGate-Induced-Drain-Leakage

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The enable circuit detects voltage collapses on VDD or VDDM rails and proactively turns on the first switch (PMOS transistor) before significant GIDL can occur. This preliminary action prevents the harmful leakage effect by restoring the conductive path before the voltage collapse completes, thereby maintaining energy savings while preventing GIDL.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The enable circuit continuously monitors the voltage levels of VDD and VDDM rails and provides feedback control to the first switch. When voltage collapse is detected, the enable circuit activates the switch to counteract the collapse and prevent GIDL. This closed-loop feedback mechanism dynamically adjusts the switch state based on real-time voltage conditions, resolving the contradiction between power savings and leakage prevention.

Inventive Principle:

Principle #23Feedback

2Loss of energy

If voltage domains are collapsed during shutdown to save energy, then power consumption is reduced, but leakage paths increase due to uncontrolled voltage transitions

Engineering Contradiction:

Improvepower consumptionVSAvoidleakage control

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The enable circuit acts as an intermediary between the voltage domains and the PMOS transistor gate. It monitors voltage conditions and mediates the switching action by turning on the transistor when voltage collapse is detected, thereby controlling the leakage path activation. This intermediary control ensures that leakage is managed systematically rather than occurring uncontrollably during voltage transitions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20240379146A1Memory power control by enable circuit

Publication Date: 2024.11.14 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A power control device includes a first switch and a second switch. A first terminal of the first switch is configured to receive a first voltage signal in a first voltage domain, and a first terminal of the second switch is configured to receive a second voltage signal in a second voltage domain different from the a first voltage domain. A second terminal of the second switch is coupled to a second terminal of the first switch, and a control circuit is coupled to control terminals of the first switch and the second switch. The control circuit is configured to turn on the first switch in response to a decrease of a voltage level of the first voltage signal.