USB Repeater Hysteresis Circuit for End-of-Packet Dribble

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Solution Overview

Problem

Conventional USB repeaters experience end-of-packet dribble (EOP dribble) in high-speed (HS) mode due to noise amplification and propagation delay, leading to spurious signal levels that can cause data corruption and link failure, without effective solutions that do not increase die area, power consumption, or require additional trim bits.

Innovation Solution

Implementing a hysteresis stage in the receiver circuit of USB repeaters to introduce an offset opposing the differential signal, reducing EOP dribble by attenuating noise without additional circuitry or power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional USB repeaters amplify differential signals in high-speed mode, then signal transmission is achieved, but end-of-packet dribble occurs due to noise amplification and propagation delay

Engineering Contradiction:

Improvehigh-speed data transmissionVSAvoiddata integrity

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The hysteresis stage is configured to detect the end-of-packet condition before the noise propagation delay causes spurious signal levels. By anticipating the EOP condition and adjusting the threshold accordingly, the system prevents dribble bits from being generated in the first place, rather than attempting to correct them after they occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The hysteresis stage dynamically adjusts the threshold parameter based on the differential signal state. During EOP conditions, the hysteresis offset prevents the amplifier from responding to noise that would otherwise cross the threshold and generate spurious output levels, thereby maintaining data integrity while preserving high-speed transmission capability

Inventive Principle:

Principle #35Parameter changes

2Reliability

If squelch detection is used to inhibit noise transmission, then EOP dribble is reduced, but propagation delay increases causing late inhibition

Engineering Contradiction:

Improvenoise suppressionVSAvoidpropagation delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

3Reliability

If additional circuitry is added to reduce EOP dribble, then data corruption is prevented, but die area increases

Engineering Contradiction:

Improvedata integrityVSAvoiddie area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The hysteresis stage is merged with the existing receiver circuitry in the USB repeater. Rather than adding a separate noise suppression module, the hysteresis function is integrated into the signal path, sharing circuit elements with the differential amplifier and threshold detection logic, thereby preventing EOP dribble without proportionally increasing die area

Inventive Principle:

Principle #5Merging (Combining)

4Reliability

If additional trim bits are implemented to adjust hysteresis, then EOP dribble is reduced, but device complexity increases

Engineering Contradiction:

Improvenoise suppressionVSAvoidconfiguration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The hysteresis stage is designed to automatically adapt to different USB speed modes (high-speed versus full/low-speed) without requiring external trim bits or configuration. The circuit self-adjusts its threshold characteristics based on the differential signal conditions, eliminating the need for complex trim mechanisms while maintaining effective EOP dribble suppression

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Effectively reduces EOP dribble in HS mode USB communications, preventing data corruption and link failure, while maintaining scalability and avoiding increased die area or power consumption.

Implementation Method 1

An offset is applied to a hysteresis stage in the receiver that is coupled to the first and second output nodes, that offset being in opposition to the differential signal generated at the first and second output nodes

Methodology Applied

Scientific EffectHysteresis: Hysteresis

Data Source

PatentUS12375127B2Rejection of end-of-packet dribble in high speed universal serial bus repeaters

Publication Date: 2025.07.29 TEXAS INSTRUMENTS INC

AI summary

Universal Serial Bus (USB) repeater circuits and methods of operating the same for communicating data signals from a first pair of data terminals to a second pair of data terminals of the repeater. In a first channel, an amplifier stage in a receiver amplifies a differential signal received at the first pair of data terminals to generate a differential signal at first and second output nodes of the receiver, and a transmitting circuit transmits a differential signal at the second pair of data terminals responsive to the differential signal at the first and second output nodes of the receiver. The receiver includes a hysteresis stage that receives an offset in opposition to the differential signal at the first and second output nodes of the receiver. End-of-packet (EOP) dribble in USB communications in the HS mode is reduced by the offset at the hysteresis stage.