Output Driving Device with Composite Transistor Slew Rate Control

Solution Overview

Problem

Conventional output drivers in semiconductor memory devices face challenges in securing a valid data period due to differences in slew rates between PMOS and NMOS transistors, leading to increased noise vulnerability and degraded input characteristics, especially during high-speed operations.

Innovation Solution

The output driving device incorporates a pull-up driver and a pull-down driver, along with a first NMOS transistor for pull-up driving and a first PMOS transistor for pull-down driving, utilizing level shift circuits to generate pre-control signals that enhance the slew rate by adjusting voltage levels, thereby complementing the slew rate characteristics of PMOS transistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the size of the PMOS transistor is increased to secure the same valid data window, then the slew rate is improved, but the output signal becomes more vulnerable to noise and input characteristics are downgraded

Engineering Contradiction:

Improveslew rateVSAvoidnoise vulnerability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent combines a PMOS transistor and an NMOS transistor in parallel configuration to form a composite pull-up driver. The PMOS transistor provides the main pull-up current while the NMOS transistor supplements it, achieving higher slew rate without increasing the size of the PMOS transistor alone, thus avoiding noise vulnerability and input characteristic degradation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent creates a composite transistor structure by merging PMOS and NMOS transistors with different electrical characteristics. This composite driver leverages the complementary strengths of both transistor types to achieve superior slew rate performance while maintaining robust noise immunity and input characteristics.

Inventive Principle:

Principle #40Composite materials

2Speed

If the size of the PMOS transistor is increased to secure the same valid data window, then the slew rate is improved, but the capacitance of the output node is increased

Engineering Contradiction:

Improveslew rateVSAvoidoutput node capacitance

Core Design Contradiction:

SpeedVSQuantity of substance

Solution Approach 1:

The patent combines a PMOS transistor and an NMOS transistor in parallel configuration to form a composite pull-up driver. The PMOS transistor provides the main pull-up current while the NMOS transistor supplements it, achieving higher slew rate without increasing the size of the PMOS transistor alone, thus avoiding noise vulnerability and input characteristic degradation.

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If a conventional push-pull driver is used, then the circuit structure is simple, but the valid data period margin is insufficient due to asymmetric slew rates

Engineering Contradiction:

Improvecircuit structureVSAvoidvalid data period

Core Design Contradiction:

Device complexityVSDuration of action of moving object

Solution Approach 1:

The patent combines a PMOS transistor and an NMOS transistor in parallel configuration to form a composite pull-up driver. The PMOS transistor provides the main pull-up current while the NMOS transistor supplements it, achieving higher slew rate without increasing the size of the PMOS transistor alone, thus avoiding noise vulnerability and input characteristic degradation.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS7440343B2Output driving device

Publication Date: 2008.10.21 SK HYNIX INC

AI summary

An output driving device includes a pull-up driver for pull-up driving an output node in response to a pull-up control signal; a pull-down driver for pull-down driving the output node in response to a pull-down control signal; and a first n-type metal oxide semiconductor (NMOS) transistor for pull-up driving the output node in response to a pre-pull-up control signal.