Push-Pull-Assisted VML Driver for High Output Swing

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Solution Overview

Problem

Existing transmitter output line drivers face challenges in achieving high efficiency without compromising signal integrity, particularly in current mode logic (CML) drivers, and in voltage mode logic (VML) drivers, which suffer from limited signal integrity and output swing.

Innovation Solution

Implementing a push-pull-assisted VML driver architecture that includes termination resistors, electrostatic discharge (ESD) resistors, and operational amplifiers to control gate voltages, allowing for adjustable current sources and supplemental current generators to enhance voltage swing and maintain signal integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If CML driver architecture is used, then signal integrity is maintained, but power consumption increases and efficiency decreases

Engineering Contradiction:

Improvesignal integrityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The driver circuit is divided into separate push-pull current sources and VML driver stages, allowing independent optimization of each section. The push-pull current sources generate supplemental currents that are injected into the VML driver output nodes, enabling the VML section to maintain signal integrity while operating at lower power consumption levels.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines CML push-pull current sources with VML driver architecture to create a hybrid system. The push-pull current sources provide the high-current drive needed for signal integrity, while the VML driver stages provide low-power operation, achieving both goals simultaneously through functional integration.

Inventive Principle:

Principle #5Merging (Combining)

2Use of energy by moving object

If VML driver architecture is used, then power consumption is reduced, but output swing and signal integrity are limited

Engineering Contradiction:

Improvepower consumptionVSAvoidoutput swing limitation

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The push-pull current sources are configured to pre-generate supplemental currents before they are needed at the output stage. These currents are stored in the current sources and then injected into the VML driver output nodes at the appropriate times, enabling the VML driver to achieve larger output swings without requiring higher operating currents throughout the entire circuit.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The push-pull current sources act as intermediary elements between the power supply and the VML driver output stage. They convert power supply voltage into supplemental currents that are then injected into the output nodes, enabling the VML driver to achieve larger output swings without directly increasing its own power consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-generated harmful factors

If higher current is used to increase output swing, then voltage swing improves, but power consumption increases

Engineering Contradiction:

Improveoutput swingVSAvoidpower consumption

Core Design Contradiction:

Object-generated harmful factorsVSUse of energy by moving object

Solution Approach 1:

Instead of uniformly increasing current throughout the entire driver circuit, the patent applies supplemental currents only at the output nodes where they are most needed for achieving larger voltage swings. This partial action approach allows the output swing to be enhanced without proportionally increasing the power consumption of the entire circuit.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The push-pull current sources operate in a periodic manner, generating supplemental currents in alternating phases that correspond to the signal transitions. During each half-cycle, one push current source generates current while the other pulls, creating periodic supplemental current injection that enhances output swing only during the periods when it is needed for signal transitions.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS12531557B2High-efficiency high-swing Voltage Mode Logic driver systems and methods

Publication Date: 2026.01.20 ANALOG DEVICES INC

AI summary

High-swing push-pull assisted Voltage Mode Logic (VML) driver circuits can enhance output voltage amplitude to improve efficiency and performance in electronic applications. For example, this is accomplished by utilizing a primary current generator circuit that is powered by a supply voltage to generate a primary current. The primary current is provided, through a switching circuit, to an output node that, in response to an input signal, generates a first output voltage. Further, a supplementary current generator circuit is coupled to the switching circuit to generate a secondary current. The combination of the primary and secondary currents increases the amplitude of the first output voltage, thereby enabling the VML driver circuit to deliver enhanced performance, particularly in applications requiring precise voltage control and high efficiency.