Flash Memory Current Sink Stabilizes Power Draw

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Solution Overview

Problem

Modern flash memory devices face security vulnerabilities due to observable drops in current consumption during programming operations, which can be exploited for unauthorized access, especially in secure integrated circuit cards like smart cards.

Innovation Solution

A flash memory device design that maintains constant current consumption regardless of the number of data bits being programmed through the use of a high voltage generator, write buffers, a current-voltage conversion circuit, and a current sink circuit, which includes a dummy cell current mechanism to stabilize current flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high voltage is used for programming flash memory cells, then programming operation can be performed, but current consumption varies depending on the number of data bits to be programmed

Engineering Contradiction:

Improveprogramming operationVSAvoidcurrent consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary anti-action by introducing a current sink circuit that actively compensates for current consumption variations before they can be observed externally. The current sink pre-adjusts the total current draw to maintain a constant level, counteracting the natural variations that would occur during programming operations with different numbers of data bits.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent changes the current consumption parameter dynamically by adjusting the current sink's operation based on the number of data bits being programmed. The system monitors programming activity and modifies the current draw accordingly, transforming a variable current consumption pattern into a constant one through active parameter adjustment.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If current consumption is reduced by programming fewer data bits, then energy efficiency improves, but security vulnerability increases due to observable current drops

Engineering Contradiction:

Improveenergy efficiencyVSAvoidsecurity vulnerability

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of variable current consumption (which creates security vulnerabilities) into a beneficial constant current profile. By using the current sink to actively manage and equalize current draw across different programming scenarios, the system transforms what would be a security weakness into a secure, uniform power consumption pattern that masks operational details.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of operation

If write buffers drive selected memory cells with program voltage, then data programming is enabled, but current consumption varies with the number of programmed cells

Engineering Contradiction:

Improvedata programmingVSAvoidcurrent consumption variation

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The patent implements feedback by having the current sink circuit continuously monitor and respond to current consumption variations caused by different numbers of data bits being programmed. The system uses this feedback information to adjust the current draw in real-time, ensuring that the total current consumption remains constant regardless of the programming operation's scale.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design enhances security by maintaining a consistent current rate, making it difficult for unauthorized access to determine which data is being programmed, thereby increasing the resistance to unauthorized access in smart cards.

Implementation Method 1

A flash memory cell, e.g., a split-gate flash memory cell uses F-N tunneling for erasing data thereof and source-side channel hot electron injection for programming data therein

Methodology Applied

Scientific EffectSource-side channel hot electron injection:

Implementation Method 2

A flash memory cell, e.g., a split-gate flash memory cell uses F-N tunneling for erasing data thereof

Methodology Applied

Scientific EffectF-N tunneling:

Data Source

PatentUS7558121B2Flash memory device and smart card including the same

Publication Date: 2009.07.07 SAMSUNG ELECTRONICS CO LTD

AI summary

A flash memory device includes an array having memory cells arranged in rows and columns. A high voltage generator is configured to supply a high voltage to the array during a programming operation. Write buffers corresponding to selected memory cells drive the selected memory cells with a program voltage or a program-inhibition voltage in response to input data. Each write buffer consumes a dummy cell current when input data is program-inhibited data. A current-voltage conversion circuit connected to the write buffers through a common sensing line supplies a current to the write buffers as the dummy cell current through the common sensing line and outputs a voltage proportional to the current, supplied to the write buffers. A current sink circuit discharges a current from an output of the high voltage generator in response to a voltage output from the current-voltage conversion circuit.