Off-Chip Driver Delay Biasing for PVT-Stable Slew Rate

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional off-chip drivers experience variations in slew rate due to process, voltage, and temperature (PVT) changes, which amplify and reduce the slew rate, leading to inconsistent performance.

Innovation Solution

The use of bias voltages to compensate for PVT variations by generating delayed voltage signals that adjust the delay between branches of the time domain stage, ensuring a controlled slew rate across different conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If delay elements are used to control slew rate, then slew rate control accuracy is improved, but susceptibility to PVT variations increases

Engineering Contradiction:

Improveslew rate control accuracyVSAvoidsusceptibility to PVT variations

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the operating parameters of the delay elements by applying different bias voltages to the delay stages. Specifically, first bias voltages are applied to a first delay stage and second bias voltages are applied to a second delay stage, allowing independent control of delay amounts. This enables the system to adjust delay parameters dynamically to compensate for PVT variations while maintaining accurate slew rate control.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If supply voltage is lowered to reduce power consumption, then energy efficiency is improved, but slew rate and delay characteristics deteriorate

Engineering Contradiction:

Improvepower consumptionVSAvoidslew rate

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The patent compensates for the deteriorated slew rate and delay characteristics at low supply voltages by adjusting the bias voltages applied to the delay stages. The control circuit modifies the delay amounts dynamically based on the actual operating conditions, allowing the system to maintain desired slew rate performance even when operating at reduced supply voltages for lower power consumption.

Inventive Principle:

Principle #35Parameter changes

3Speed

If delay between branches is increased to control slew rate, then slew rate is reduced, but delay sensitivity to PVT variations is amplified

Engineering Contradiction:

Improveslew rateVSAvoiddelay stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent segments the delay control into multiple independent delay stages, where each stage can be controlled by separate bias voltages. This segmentation allows the control circuit to adjust each delay stage independently, compensating for PVT variations that affect different branches differently, thereby reducing the amplification of delay sensitivity while still achieving the desired slew rate control.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8098083B2Apparatus and method for controlling delay stage of off-chip driver

Publication Date: 2012.01.17 NAN YA TECH

AI summary

A multiple-finger off-chip driver (OCD) uses delay between branches of the output stage. The delay between branches is controlled using bias circuitry which compensates for process, temperature, and voltage (PVT) variations, resulting in less variation of slew rate at the output of the OCD. The OCD includes a time domain delay stage; a pre-driver stage; a final driver stage; and a bias circuit, for providing bias voltages to the time domain stage that compensate for process, temperature and voltage (PVT) variations on the time domain stage.