LVDS Driver Circuit Topology for Low Power and Impedance Matching
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Solution Overview
Problem
Conventional low voltage differential signal (LVDS) driver circuits face challenges in minimizing power consumption while maintaining proper impedance matching and avoiding large input capacitances.
Innovation Solution
A low voltage differential signal driver circuit topology is implemented, featuring a differential current mode amplifier pre-driver stage and a differential voltage mode amplifier output stage, where the total current consumption equals the load current plus a minimal additional current used by the pre-driver stage, with impedance matching achieved through resistances and transistor configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a current mode output stage is used to achieve good line impedance matching, then impedance matching is improved, but power consumption increases
Solution Approach 1:
The output stage is divided into two separate current mode push-pull stages (first and second current mode output stages) that operate at different times. The first stage drives the load during one half-cycle while the second stage remains inactive, and vice versa. This segmentation allows each stage to be optimized for low power consumption while collectively providing continuous drive capability with proper impedance matching to the differential transmission line.
2Use of energy by moving object
If supply current is reduced to minimize power consumption, then power consumption is reduced, but the ability to drive the load impedance effectively is compromised
Solution Approach 1:
The circuit employs periodic action by alternating between two current mode output stages in a push-pull configuration. Each stage conducts current during alternate half-cycles of the differential signal, allowing the load to be driven effectively throughout the entire cycle while each individual stage operates at reduced current levels, thereby minimizing overall power consumption while maintaining load driving capability.
3Use of energy by moving object
If a voltage mode driver is used to achieve low power consumption, then power consumption is reduced, but line impedance matching deteriorates
Solution Approach 1:
The invention changes the operating parameter of the output stage from voltage mode to current mode, specifically using current mode push-pull stages that can simultaneously achieve low power consumption and proper impedance matching. The current mode operation allows the output impedance to be matched to the differential transmission line impedance (typically 100 ohms) while consuming minimal power, resolving the contradiction between power consumption and impedance matching that plagues voltage mode drivers.
Data Source
AI summary
A low voltage differential signal (LVDS) driver circuit with reduced power consumption. A pre-driver stage, implemented as a differential current mode amplifier, is driven by the differential input signal and provides a corresponding differential drive signal, which drives the output stage, implemented as a differential voltage mode amplifier, which, in turn, provides the differential output signal for the load. Total current consumption equals the load current, which is provided by the output stage, plus a much smaller current used by the pre-driver stage.