On-Chip Temperature Sensing for DRAM Refresh Power Control

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Solution Overview

Problem

Semiconductor memory devices, such as DRAMs, face challenges in power consumption due to temperature-dependent characteristics, requiring frequent refresh operations that increase power consumption, and existing temperature detectors have non-linear temperature sensing and are limited to a single target temperature.

Innovation Solution

A temperature sensor system utilizing a PTAT current generator, a first CTAT current generator, and a second CTAT current generator to generate currents proportional and inversely proportional to temperature, converting these currents into a signal for accurate temperature detection, allowing for linear temperature sensing across a range of temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If refresh operations are increased to maintain data integrity at high temperature, then data sustain time is improved, but power consumption increases

Engineering Contradiction:

Improvedata sustain timeVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic refresh control by adjusting the refresh period based on detected temperature. The refresh control unit varies the refresh period according to temperature conditions, enabling the system to adapt refresh frequency to actual thermal states rather than using a fixed periodic refresh schedule.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the refresh period parameter based on temperature detection. The refresh control unit modifies refresh operation parameters (period/frequency) according to the temperature signal from the temperature detector, optimizing the balance between data integrity and power consumption under different thermal conditions.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If refresh period is increased to reduce refresh clock frequency in low temperature region, then power consumption is decreased, but data sustain time is reduced

Engineering Contradiction:

Improvepower consumptionVSAvoiddata sustain time

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The system dynamically adjusts the refresh period based on real-time temperature detection. In low temperature regions, the refresh period is increased to reduce power consumption, while in high temperature regions, the refresh period is decreased to maintain data integrity, creating a temperature-adaptive refresh strategy.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The refresh period parameter is changed according to temperature conditions. The refresh control unit modifies this parameter based on temperature detector output, allowing the system to optimize between power consumption and data sustain time by varying the refresh frequency match to thermal environment.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If conventional temperature detector with multiple current generators is used, then temperature detection capability is improved, but device complexity increases

Engineering Contradiction:

Improvetemperature detection capabilityVSAvoidcircuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines PTAT and CTAT current generators into a single integrated temperature detector circuit. The detector includes both current generator types working together, with their outputs fed to a comparator that determines temperature based on the relationship between the two current signals, achieving accurate temperature detection through circuit integration.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The temperature detector uses feedback from the relationship between PTAT and CTAT currents to determine temperature. The comparator monitors the ratio or difference between these two temperature-dependent currents and generates a temperature indication signal based on their comparison, creating a self-referencing temperature measurement system.

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

Enables efficient power management by accurately detecting temperature, optimizing refresh operations and reducing power consumption in semiconductor memory devices through linear temperature sensing across a wide range.

Implementation Method 1

a proportional to absolute temperature current generator (referred to as 'PTAT current generator' hereinafter) 210

Methodology Applied

Scientific EffectProportional to Absolute Temperature (PTAT) effect:

Implementation Method 2

a complementary to absolute temperature current generator (referred to as 'CTAT current generator' hereinafter) 220

Methodology Applied

Scientific EffectComplementary to Absolute Temperature (CTAT) effect:

Data Source

PatentUS7532056B2On chip temperature detector, temperature detection method and refresh control method using the same

Publication Date: 2009.05.12 SAMSUNG ELECTRONICS CO LTD

AI summary

A temperature sensor includes a proportional to absolute temperature (PTAT) current generator configured to generate a first current proportional to temperature, a first complementary to absolute temperature (CTAT) current generator configured to generate a second current inversely proportional to temperature, a second CTAT current generator configured to generate a third current inversely proportional to temperature, and a temperature sensing unit configured to convert the first current, the second current, and the third current into a signal related to the temperature.