LVDS Driver Feedback Control for High-Impedance Mode Switching

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Solution Overview

Problem

Existing LVDS driver circuits face issues with power consumption during high impedance mode due to continuous current flow through bypass circuits, leading to increased power consumption and potential overshoot in output signals when switching modes.

Innovation Solution

The LVDS driver circuit incorporates a feedback control circuit that sets a higher control voltage in high impedance mode, ensuring the transistor is turned on during mode switching, preventing overshoot and reducing power consumption by eliminating unnecessary current flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a bypass circuit is used to enable high impedance output in LVDS driver circuit, then the output can be set to high impedance state, but power consumption increases due to continuous current flow through the bypass circuit

Engineering Contradiction:

Improveoutput impedance controlVSAvoidpower consumption

Core Design Contradiction:

Ease of operationVSUse of energy by stationary object

Solution Approach 1:

The patent extracts the harmful continuous current flow from the bypass circuit by introducing a switching element that disconnects the current path during high impedance mode, eliminating unnecessary power consumption while maintaining the high impedance output functionality

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent makes the circuit configuration dynamic by using a switching element that changes the circuit topology based on the output mode (signal output mode vs. high impedance mode), allowing the circuit to adapt its current flow characteristics to the required operating state

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If mode switching is performed in LVDS driver circuit, then output mode can be changed, but overshoot occurs in output signals during mode transitions

Engineering Contradiction:

Improvemode switching capabilityVSAvoidsignal stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-charging or pre-discharging capacitive nodes before mode switching occurs, or by sequentially switching elements to prepare the circuit state in advance, thereby preventing voltage overshoot during the transition from signal output mode to high impedance mode

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent provides beforehand cushioning by introducing damping elements or controlled discharge paths that absorb or dissipate excess energy during mode transitions, preventing signal overshoot and protecting the circuit from voltage spikes

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS11043935B2LVDS driver circuit, integrated circuit device, oscillator, electronic apparatus, and vehicle

Publication Date: 2021.06.22 SEIKO EPSON CORP

AI summary

An LVDS driver circuit includes: a current source; a differential unit configured to receive a first input signal and a second input signal and output a first output signal and a second output signal; and a feedback control circuit configured to be coupled to a first output node and a second output node and to perform, by outputting a control voltage to a gate of a transistor, feedback control that sets a common voltage of a differential output signal. In the differential unit, the first output node and the second output node are in a high impedance state in the high impedance mode, the differential unit is configured to output the first output signal and the second output signal in the signal output mode, and the control voltage in the high impedance mode is larger than the control voltage in the signal output mode.